continued to add gpu based convolution api, build is broken in this commit
added header files for gpu api
moved operator<< out into it's own compilation unit (needed to adapt cmake files), gpu api in place, library compiles and links (still need to address boost finding issue, gpu code untested)
BOOST_ROOT picked up alright by cmake build system
fixed cmake files to pick up non-standard boost installation
gpu api inplace and tested on small datasets
replaced synch by asynch memory transfers