Implemented bulk email interface for new dashboard
disable buttons for large courses on legacy and beta instr dash

set max enrollment for downloads to 200
Implemented bulk email interface for new dashboard

Responses to Adam's comments; reset common.py, i18n compliance, deleted extraneous email.html file, fixed an HttpResponse, deleted unnecessary commented-out code, some small style tweaks
Changed GET to POST and xmodule HTML editor call, section CSS
Added acceptance tests for bulk email (through beta dashboard)
Merged in email confirmation modal
API tests, email tests, working notifications
added self to authors style, changed GET to POST
Re-added legacy email tests, wrapped up last few bugs, cleaned up CSS
Response to Sarina's comments
Response to Will's comments
Fixed HTML editor on old dash; improved warning messages