Support returning full_name (and SLID) for LLCacheName::get() calls

Changed callback signature to full_name instead of first_name,last_name
Eliminated all calls to legacy (non-signal/non-boost-bind) lookup mechanism
Change Pay dialog names to SLURL links
Tweaked layout of Pay Resident and Pay via Object floaters to make SLURLs fit
Consolidate name first + " " + last concatenation in LLCacheName::buildFullName()
Reviewed with Kelly