Added drop-down editing menu for admin users.
Remove dropdown on edit menu, and make it actually work.
refactor page layout to store blocks separately and support multiple blocks in a column
highlight entire column for left/right position
fix test data
include cancel/save buttons in layout editing toolbar
fix cancel while adding block, fix dragging block buttons in ff
make sure it's still possible to drag text in contenteditables
make sure text can be selected in ff
handle enter key while entering search term, refs 1558
show title instead of listing in object picker, since the latter doesn't always work
handle dropping on cols/rows/layout in addition to on blocks
adjust edit menu to get actions from context
supply default layout a different way to work around possible bug in react-forms
Source is already required for construct, so just adding to list.
Merge pull request #324 from ENCODE-DCC/1522-layout-refactor

Switch to new way of storing layout
Merge pull request #325 from ENCODE-DCC/1413-construct-source

Source is already required for construct, so just adding to list. #1413
Merging in master.
Bringing in new Jest tests from 1567-expdate branch; adding PM refs Jest tests.