make sure toolbar view is created only once, and also renders immediately
enable multi-select for box select tool
basic plumbing for poly selection on marker glyphs

Still needed:

* improved poly selection overlay UI interactions
* "reset/new poly" without clearing selection
* styling for overlay
* hit testing on more glyph types
basic lasso tool implementation
restore rule at toolbar edge
adding icons for lasso and poly tool
Merge branch 'feature/more_tools' of https://github.com/ContinuumIO/bokeh into feature/more_tools
changing tool active state clears overlay
update to latest hammer.js
enable enter and double click to clear poly/lasso overlays
Merge master
must init display defaults on demand, init is potentially too late
add some logging
lasso tool should clear overlay on pan end
plumbing to make appearance of plot selection overlay configurable
Merge branch 'master' into feature/more_tools
Preliminary type-driven JSON deserialization
updating tool icons
updating to address issues #1299 and #1313
Fix name errors in Dict.from_json()