Show datasets bounding box

[matthewma7]

This PR implements a new feature that shows boundaries of selected datasets. It uses colors from colorbrewer.pastel1 series for box filling and geojs AnnotationLayer for labeling.

I feel this feature along with previous features regarding datapanel change is asking for more expressive icon usage, specifically stacked icon. The base girderfontello doesn't support stacked icon, but I think I'd introduce stacked icon to minerva in later PR.

This PR also moves the two buttons on Dataset panel title onto action panel.

[codecov-io]

Codecov Report

Merging #468 into master will increase coverage by 2.22%. The diff coverage is 80.18%.

@@            Coverage Diff             @@
##           master     #468      +/-   ##
==========================================
+ Coverage   44.35%   46.58%   +2.22%     
==========================================
  Files          72       72              
  Lines        3506     3598      +92     
  Branches      297      301       +4     
==========================================
+ Hits         1555     1676     +121     
+ Misses       1951     1922      -29

Impacted Files	Coverage Δ
web_external/views/widgets/DatasetInfoWidget.js	5.26% <0%> (-0.3%)	:arrow_down:
web_external/views/map/MapPanel.js	54.47% <100%> (+9.83%)	:arrow_up:
server/rest/dataset.py	66.09% <66.66%> (+2.18%)	:arrow_up:
web_external/views/body/DataPanel.js	47.7% <93.54%> (+18.41%)	:arrow_up:
web_external/views/body/SessionView.js	43.29% <0%> (+1.03%)	:arrow_up:
web_external/models/DatasetModel.js	61.11% <0%> (+3.96%)	:arrow_up:
web_external/models/SessionModel.js	58.69% <0%> (+6.52%)	:arrow_up:
web_external/collections/DatasetCollection.js	93.33% <0%> (+26.66%)	:arrow_up:

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[matthewma7]

Hi @manthey, thanks for your review suggestions. I have made the changes accordingly.