[FEATURE] Build System: added macro seqan_setup_cuda_vars()

Squashed commits:
[1721c1c] [FIX] Build System: fixed CUDA on MacOS X
[FIX] Index: qualified indexRawText() as host-device
[INTERNAL] ContainerView: asserted value() and getValue()
[FIX] CUDA Misc: removed one warning
[INTERNAL] Shape: qualified weight() and length<Shape>() as host-device
[API] FMIndex: added operator[] to FibreLF
[INTERNAL] FMIndex: added a header file with supported device types
[API] Basic: added metafunction MinLength<>::VALUE
[TEST] CUDA: added Index tests
[INTERNAL] CUDA Demos: removed count() from counting demo
Merge pull request #35 from esiragusa/test/cuda/index

Test FMIndex on CUDA