Performance enhancement targeted at the physical pathfinding algorithm.

 * Add methods to convert a MAC/GUID to and from string and integer representations (for lookup table keys)
 * Extend the functionality of the lookup table interface to support explicit keys, replace, remove.
 * netloc_data_collection_handle_t now uses the lookup_table for both edges and nodes.
 * Cache the integer representation of the MAC/GUID on the netloc_node_t structure.
 * Remaining todo item to add a proper hashing mechanism to the lookup table for string based keys.
 * Add a progress reporting mechanism to the netloc_reader_ib (CLI --progress | -p)
(cherry picked from commit 20cbe75149dac3cc86cb777625284b2f4a7f4a0b)
0.5rc1 is out; on to 0.5rc2