Implement system of profiles for project settings.

Now it is possible to force particular profile to use for rendering (--profile option).

==================================
Sample contents of project.conf:
==================================
[main]
active_profile=draft-lq

[draft-lq]
WIDTH=480
HEIGHT=270
FPS=25
FORMAT=avi
AUDIO_RATE=48000
blender.cycles_samples=10

[draft]
WIDTH=480
HEIGHT=270
FPS=25
FORMAT=avi
AUDIO_RATE=48000
blender.cycles_samples=100

[hd]
WIDTH=1280
HEIGHT=720
FPS=25
FORMAT=avi
AUDIO_RATE=48000
blender.cycles_samples=100
==================================