Added README.

README.md

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+# Overview
+This repository bundles all the [CommsChampion Ecosystem](https://commschamp.github.io/) projects
+into a single CMake one. It is expected to be used in another CMake project that has some
+[CommsChampion Ecosystem](https://commschamp.github.io/) dependencies and built using
+the [ExternalProject_Add()](https://cmake.org/cmake/help/v3.15/module/ExternalProject.html) cmake
+function with an appropriate configuration.
+
+# CMake Configuration
+The major [CMakeLists.txt](CMakeLists.txt) contains a list of supported options and other
+configuration variables. All the projects are disabled by default. The CMake invocation is
+expected to use [CMAKE_PROJECT_INCLUDE](https://cmake.org/cmake/help/v3.15/variable/CMAKE_PROJECT_INCLUDE.html)
+variable pointing to a file, which lists all the required projects to get compiled.
+
+If one of the selected project depends on another (see [DefaultConfig.cmake](DefaultConfig.cmake) for details),
+the latter gets built even if it was not explicitly enabled.
+
+The configuration file provided via the [CMAKE_PROJECT_INCLUDE](https://cmake.org/cmake/help/v3.15/variable/CMAKE_PROJECT_INCLUDE.html)
+variable can also override / update the default configuration provided by this project by
+setting appropriate variables.
+
+The supported variables are:
+
+- `<PROJ_NAME>_SOURCE_DIR` - Override the default source directory.
+- `<PROJ_NAME>_GIT_REPOSITORY` - Override the default project repository URL. To
+  disable usage of the repository and use source directory (set by the `<PROJ_NAME>_SOURCE_DIR`)
+  instead, set the `<PROJ_NAME>_GIT_REPOSITORY` value to `_`.
+- `<PROJ_NAME>_GIT_TAG` - Override the default tag.
+- `<PROJ_NAME>_CMAKE_ARGS` - Extra CMake arguments to be passed to the project. Use
+  only project specific configuration, no need to set variables like
+  [CMAKE_GENERATOR](https://cmake.org/cmake/help/v3.15/variable/CMAKE_GENERATOR.html),
+  [CMAKE_BUILD_TYPE](https://cmake.org/cmake/help/v3.15/variable/CMAKE_BUILD_TYPE.html), or
+  [CMAKE_CXX_STANDARD](https://cmake.org/cmake/help/v3.15/variable/CMAKE_CXX_STANDARD.html). They
+  are all automatically inherited from this project.
+
+The `<PROJ_NAME>` prefix is combined by the project name capitalized and every `.` (dot) character
+replaced with the `_` (underscore). For example:
+
+- [cc_tools_qt](https://github.com/commschamp/cc_tools_qt) becomes `CC_TOOLS_QT`.
+- [cc.mqtt5.generated](https://github.com/commschamp/cc.mqtt5.generated) becomes `CC_MQTT5_GENERATED`.
+- [cc.mqtt5_client_filter.cc_tools_plugin](https://github.com/commschamp/cc.mqtt5_client_filter.cc_tools_plugin)
+  becomes `CC_MQTT5_CLIENT_FILTER_CC_TOOLS_PLUGIN`
+
+
+For example to enable the MQTT5 client library
+(see [cc.mqtt5.libs](https://github.com/commschamp/cc.mqtt5.libs))
+while disabling build of provided client applications, the
+configuration file can have the following lines:
+```
+set (OPT_CC_MQTT5_LIBS ON)
+list (APPEND CC_MQTT5_LIBS_CMAKE_ARGS -DCC_MQTT5_CLIENT_APPS=OFF)
+```
+
+In case a value of one of the variables provided via the `<PROJ_NAME>_CMAKE_ARGS` needs to
+contain a CMake list, then the separation of the values needs to be performed using the
+`|` character instead of usual `;`.
+
+```
+list (APPEND CC_MQTT5_LIBS_CMAKE_ARGS -DCC_MQTT5_CUSTOM_CLIENT_CONFIG_FILES="/path/to/config1|/path/to/config2")
+```
+
+# Third Party Dependencies
+
+## Qt Dependency
+Some projects (mostly [cc_tools_qt](https://github.com/commschamp/cc_tools_qt) and the relevant plugins) depend
+on the Qt library. To provide a path to the compiled libraries (required mostly on Windows platform) use
+standard [CMAKE_PREFIX_PATH](https://cmake.org/cmake/help/v3.15/variable/CMAKE_PREFIX_PATH.html) variable
+passed to this project. It will be propagated to all other projects.
+
+All the projects in the [CommsChampion Ecosystem](https://commschamp.github.io/) are expected
+to support both Qt5 and Qt6. To overwrite the default Qt major version (currently Qt5) use the
+`OPT_QT_MAJOR_VERSION` CMake variable.
+```
+cmake -DOPT_QT_MAJOR_VERSION=6 ...
+```
+
+## Boost Dependency
+Some projects (mostly command line applications in the libraries projects) depend on [Boost](https://www.boost.org/).
+It is expected to use the relevant variables described in the [FindBoost](https://cmake.org/cmake/help/v3.15/module/FindBoost.html)
+documentation to help with finding appropriate boost libraries. All the passed boost configuration variables will be passed
+to the relevant projects as well.
+```
+cmake -DBOOST_ROOT=C:\boost -DBoost_USE_STATIC_LIBS=ON ...
+```