Fix comparer bug on split screen

Split Screen mode would share and otherwise disrupt the "selected"
graphics from one map to another.  The containers and layer were
initialized when the class was loaded instead of when an instance
was created, so they were actually shared between map panes.  They
are now initialized in the constructor to be unique.
Merge pull request #184 from mmcfarland/bugfix/phantom-selection-comparer

Fix comparer bug on split screen
Move Identify to its own file
Disambiguate tryIdentify from doIdentify
Allow plugins 5 seconds to identify before timeout

5 seconds was chosen arbitrarily, to prevent indefinite requests. I found 350 milliseconds to be the sweet spot where some Layer Selector requests fail and some succeed, at least for AGS servers. This variable can be configured over time.
Fix invalid reference
Merge pull request #183 from steventlamb/topic/debug_identify

Topic/debug identify