Implement multi-region PVT for all property classes

since they are not using a single PVT table anymore, their "Single"
prefix has been removed...
incorperate the review comments/decisions for multi-region PVT

the largest change is that all classes below opm/core/props/pvt take
the PVT region index as an argument, the higher-level ones (i.e.,
BlackoilProps*) take cell indices.
handle the case that the compressed to logically cartesian array is NULL
add an assert
add missing PVTW keywords to the decks used by the equil test

the test still fails, but the errors seem to be due to differences in
the saturation functions...
fix the equilibration test by using new values

thanks to @bska for the hints.
add missing include

for some reason this seems to be only required by GCC 4.4
change item names used to query the PVCDO keyword

That's similar to having fun with a vodoo doll...
Merge pull request #587 from andlaus/implement_multi-region_pvt_tables

Implement multi-region PVT properties