Read raw banks from MDF

I've included a small library for reading mdf files in the mdf directory.

• zlib compression is enabled by default and zlib must be present
• lzma and lz4 are available as configure options -DUSE_LZMA and -DUSE_LZ4
• some reorganization of the CMake files to avoid rebuilding files when building tests
• A test has been added that dumps the banks. The files are identical to the bin files already in use
• Add FindTBB.cmake to allow TBB to be picked up from LCG
• Add a command line option and some printout to select the device on a multi-GPU system

Reorganised InputReader a bit, please have a look and feel free to comment, it's a bit of a cludge.

Apologies for the big MR.

P.S. The latest ROOT built with LCG_94 requires C++17, so we can't build with that one.

Closes #26 (closed), #27 (closed)