Don't store rendering mode in Texture

If this is a property of the texture itself, that fact should be stored
in the texture metadata. If it's a property of rendering, we should note
that when it's rendered, as we do after this commit.
Fix format specifiers for long longs
Merge pull request #44 from svkurowski/fix_format_specifiers

Fix format specifiers for long longs
travis: now prints python3 --version instead of python --version

we don't really care about the python2 version
travis: fixed build

travis's ubuntu 12.04 gcc/glibc appears to be sufficiently ancient to not support <inttypes.h> PRId64 for -std=c++11
added workaround using casts.
travis: hopefully fixed build now...

python3 didn't exist at the point where I ran python3 --version...
job: added documentation
project: improved license files

GPLv3 is now stored in LICENSE
added COPYING.md, with a list of 3rd-party files
doc: fixed link to copying.md in README.md
Merge branch 'master' of github.com:SFTtech/openage
buildsystem: added more fixes to python.cmake

this should fix an issue that was reported with ubuntu 13.10

PYTHONLIBS_VERSION_STRING ended with a plus sign, which caused find_package(PythonInterp) to fail.
This hack strips away any trailing garbage.
project: added cmake modules to BSD-license list in copying.md

also did some style fixes to copying.md
project: added info on per-file legal texts to copying.md
project: refined per-file legal text block policy
Add AssetManager

AssetManager owns textures and is responsible for loading them, or
loading the new 'missing' texture if the file is unavailable.
Use AssetManager in Terrain
Implement Texture reloading
Use inotify to monitor for changed assets
readme: removed flattr button as it does not support group repos

Linus Olsson:
Sorry but project pages on github can't be flattred. All our connections
are built on us asking the service API who the owner is. Github project
does not have an owner. So we can't know who should have the money :(
legal: re-wrote copying.md, added 3rd-party licenses

added detailed guidelines to copying.md.