Bug 893276: Only write simple-storage to disk after it has been changed.
Merge with master
Switch to using fs APIs for file reading and writing.
Bug 854226 - keep check of widgets having been inserted by id, r?zer0
Implement viewFor(window) support.
Merge pull request #1300 from gijsk/854226-widget-restart-adding

Bug 854226: keep check of widgets having been inserted by id. r=zer0
Merge pull request #1301 from Gozala/bug/window-getView@695143

Bug 695143 - Implement viewFor(window) support. r=@ZER0
Address review comments by logging errors and catching them in tests and updating the hash at the end of successful writes only.
Merge pull request #1134 from Mossop/bug893276_2

Bug 893276: Only write simple-storage to disk after it has been changed. r=@gozala