bug 1280894, make AddRemove sort stable without map hacks, r=stas The logic to have ordering for AddRemove given externally was a hack, in hindsight. This patch makes AddRemove stable given two iterables, and adds tests to verify that. The test fixes are OK, as the ordering there is for the same position in the localization, and it's kinda ambiguous which should come first or not. This is in support for elmo fluent diffs, 'cause then I can use AddRemove easier there for both keys and attr names. MozReview-Commit-ID: 2NEW4lCxW5M

bug 1280894, expose attributes on FluentEntity, r=stas For the elmo diff, it's going to be nice to have access to a wrapper for Attribute nodes. MozReview-Commit-ID: LASd3iiJJJ6