Merge pull request #10407 from asutherland/email-progress-spinner. r=jrburke, a=blocking-b2g=leo+

Bug 882994 - [email] UI: Replace sync progress bar (including candy bar) / messages spinner with single spinning refresh button. r=jrburke(cherry picked from commit 9f283ab5e6b2e49513057138eacaa6adaff488ac)

Conflicts:
	apps/email/style/message-cards.css