Add Feature Compare plugin

Given a configuration of URLs that are capable of being displayed
as ESRI FeatureLayers, this plugin allows you to select features
from the map and compare their attributes.  It supports state and
export features from the framework, but has some additional
features to be added (support for older browsers, formatting of
attribute values) that will be added feedback from the client
Merge pull request #180 from mmcfarland/topic/watershed-compare

Add Feature Compare plugin
Provide handle for moving panels

Use the header for legend and plugin panels to do the moving.
This is both a little more intuitive and happens to resolve
an issue with the body of the element being dragged consuming
events meant for child form elements in the container.
Merge pull request #181 from mmcfarland/topic/draggable-handles

Provide handle for moving panels
Use TNC AGS for printing

The sampleserver6.arcgisonline.com Print Task was very unstable.
Merge pull request #182 from mmcfarland/topic/new-print-server

Use TNC AGS for printing
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