remove USE_FP_LIB_TABLE code, make it the norm.  Add lazy loading support to FOOTPRINT_INFO.
Pcbnew: Geda plugin fixes.

* Prevent cache from being reloaded on every footprint file read.
* Fix a bug forming wxFileName in GPCB_FP_CACHE::Load().
* Fix invalid file name time stamp debug assertion.
* Use FPID to set loaded footprint name.
* Remove file name <> from exception strings per UIPolicy.