This commit brings many changes:
1. Remove cotire;
2. Remove PCH files (stdafx.xxx) and mentions;
3. Rearrange and clean includes:
3.1. Remove core includes path, use full header path core/xxx;
3.2. Move object_ptr to separate file base/object_ptr.h;
3.3. Add missing includes;
5. Add forward decls;
6. Get rid of some Qt private parts;
7. Fix ALL compilation errors after removing cotire on Windows, Linux, MacOS.
Closes#133.
Related to #96.
Media::Player::Widget displays the current voice / video message
if it is played and the current song otherwise.
It is created when a voice / video message starts and is destroyed
when all the voice / video messages in the playlist are finished.