Specify full path in #include.

This is required for an upcoming application.
It was already discussed in #89 and will come up
with more changes as the application grows. So
step by step all #includes will have the full
paths prepended.
[IO] Clarify which mesh file was read.
[ML] Specify full path for some includes.
Consistent copyright year 2012-2014.
Merge pull request #452 from endJunction/Cleanup

Cleanup
[bugfix] fixed issue where raster to mesh conversion would fail if all all intensity values were negative
Merge branch 'master' of https://github.com/ufz/ogs