Fix Windows file associations creation.

Now qBittorrent create global ProgId during installation (using HKLM hive)
and allow to associate .torrent files with it (using HKCU).

Conflicts:
	src/preferences/preferences.h
	src/windows/installer.nsi
	src/windows/uninstaller.nsi
Truly sync the changes in the file assocations code/installer with master.
Sync translations from Transifex and run lupdate.
Fix again libtorrent 0.15.x compilation.
Update Changelog.
Bump to 3.1.10