MVE: App scene2pset updated
DMRECON: precompute srgb2lin mapping

Computing this on demand leads to nasty race conditions and 256 floats
are not _that_ much, so use a precomputed table instead of protecting
it with a mutex.
Merge pull request #40 from Waldteufel/srgb2lin

DMRECON: precompute srgb2lin mapping
DMRECON: Small style change
APPS: Parallelized scene2pset with OpenMP statements
MVE: Added generic attribute 'value' to TriangleMesh, updated PLY reader and writer