Adds session states.

You can save/load sessions with the core saveSession and loadSession
May be buggy right now.
Report every bug you find, please.
Fixes auto-pausing.
Fixes build
Remove a debug output line
Merge branch 'master' into wip/savestate
Merge branch 'master' into wip/savestate

Conflicts:
	src/Core.cpp
	src/Torrent.cpp
Several changes

Change return of loadSession
Change names of variables.
Made error messages a bit more informative.
Add function prototype and some notes
Make loadSession create a session if no folder is found.
Make loadSession not complain instead
Fix all typos and compile errors
Use checkDirExist instead of stat
Merge pull request #54 from gtorrent/wip/savestate

Adds session states.