inventory: use standard AppDataLocation for model files

This puts the models in $XDG_DATA_DIR/translateLocally on Linux,
or equivalent user data directories on other platforms.

This avoids putting relatively large files in the config directory,
which may be versioned for user dotfiles.

Github: closes #139

src/inventory/ModelManager.cpp

@@ -7,6 +7,7 @@
 #include <QDirIterator>
 #include <QFile>
 #include <QSaveFile>
+#include <QStandardPaths>
 #include <QFileInfo>
 #include <QJsonDocument>
 #include <QJsonObject>
@@ -77,9 +78,7 @@ ModelManager::ModelManager(QObject *parent, Settings * settings)
     , settings_(settings)
     , isFetchingRemoteModels_(false)
 {
-    // Create/Load Settings and create a directory on the first run. Use mock QSEttings, because we want nativeFormat, but we don't want ini on linux.
-    // NativeFormat is not always stored in config dir, whereas ini is always stored. We used the ini format to just get a path to a dir.
-    appDataDir_ = QFileInfo(QSettings(QSettings::IniFormat, QSettings::UserScope, "translateLocally", "translateLocally").fileName()).absoluteDir();
+    appDataDir_ = QStandardPaths::writableLocation(QStandardPaths::AppDataLocation);
     if (!QDir(appDataDir_).exists()) {
         if (QFileInfo::exists(appDataDir_.absolutePath())) {
             std::cerr << "We want to store data at a directory at: " << appDataDir_.absolutePath().toStdString() << " but a file with the same name exists." << std::endl;