runtime: added support for setting thread affinity to all blocks under a hier_block2.

grc: added field to all blocks to set the thread affinity to a list of processors.

docs: updated docs on thread affinity for new features.

Conflicts:

	grc/base/Block.py
	grc/python/flow_graph.tmpl
Applying hidapi patch from  Hans de Goede
Merge branch 'maint'
build: attempting better handling of ICE libraries.

Also allow easy use of Ice 3.5 (default if found).