Version 0.5.3

This is a "sustaining" release of 0.5.x branch, with ABI and API compatibility still retained but quite a few improvements backported from the upcoming 0.6 version. Here's the list:

• (#301/#383) Room::aliases() and Room::setAliases() are fixed, using the new alias management introduced in MSC2432 - thanks to @ram-nad
• (#321) More careful linkification of Matrix ids
• (#326) Support for the server notices room tag (MSC1452)
• (#330) Support of resolving the homeserver using .well-known (MSC433) - thanks to @encombhat
• (#341/#373/#376) Support of message editing and annotation (MSC1849) - thanks to @rpallai
• (#344) Compatibility with user deactivation error codes (MSC2181)
• (#345) Fix cache becoming inconsistent with actual room state due to unread counts not properly tracked - thanks to @rpallai
• (#347) Fix for a corner case in internal user avatar management that may lead to a crash in rare cases
• (#354) Provide a means to get the full list of rooms to client applications (aimed at fixing quotient-im/Quaternion#637 in the next Quaternion 0.0.9.4 rebuild)
• (#358) Only send access token where the spec says that it should be sent - thanks to nepugia for reporting
• (#359) Fix room highlighting for names with a hashtag - thanks to @a-andreyev
• (#361) Initialise read marker if there's none on the room yet
• (#365) Remove prev_content from special keys preserved against redaction (MSC1954)
• (#366) Make downloaded file name building more robust - thanks to nepugia for reporting
• (#387) Compatibility with Qt 5.14
• (#386/#388) SSO support
• (#390) Notify the client application about alias updates

Many thanks to everybody who tests and helps with development - and a separate thanks for the patience of users waiting for so long to get this release! You all are awesome!

P.S. The name of the library in this branch is still libQMatrixClient. Version 0.6 will be named libQuotient, as announced previously.