Last-minute wishes for the next map format

[stef]

I've removed the particle emitter (and put it in it's own branch), because at this time, AC doesn't have any particles, that could be useful for mapping. Once someone implemented a few nice particles, the emitter can easily be put back. It doesn't require a map format change.

Instead, I added rotated and tilted clip entities. http://i.imgur.com/pLyUtXH.jpg http://i.imgur.com/sTB0q4n.jpg

All changes can be seen here: https://github.com/ac-stef/AC/commits/mapformat10

Since there seems to be no interest in new features that require map format changes, I'd say, that map format 10 is now complete and can be merged into "next". After some more testing, of course...