AnyUnitSize merge: refactoring and cleaning up

See merge request maxr/maxr!15

These are small scale fixes I've made in AnyUnitSize branch:

 - Removed global Quit method. Event manager exits its event loop more gracefully.
 - Moved utlities like pcx, unifonts, tinyxml to appropriate folder
 - Global `cUniFont font;` has ben moved to static field inside cUniFont.
 - removed `#include "gameversion.h"` from netmessage2.h. It caused massive rebuilds after every git change.
 - updated paths to tinyxml2.h. It will not collide with system-wide version.

- Remove dependency to user installed compiler
- Add tag to make sure the job gets executed on a valid runner (in preparation to future runners on other platforms)

Fix gcc 8.1 build

See merge request maxr/maxr!16

removed pointer Job* from cUnit, as this introduced circular references between game objects, which cannot be deserialized. The pointer wasn't needed anyways...

improved surveyor ai: it now plans the whole move for the turn at once. Also plans more efficient routes, so it will survey more field per turn.