Bulk update works as well

Fix underscore template error.
Fix `=` spacing

Add user avatar to user selection

Milestones needed a none selector
Assignee needed unassign.

Added nice animations too.

Using respond to instead

Make add single and add multi work properly.
Multiple inputs for multiselect

Adds deselect still a WIP.

Clarify LFS configuration

A user on Twitter was confused (rightfully so) because LFS admin docs suggest you must set a storage path. In fact, Omnibus defaults to a very sane location. Add a comment to the snippet outlining the default.

See merge request !3388

Fix cancel button on issuable edit form

See merge request !3392