Sort all fields in alphabetical order to make the diffs deterministic

Currently the jinja template generates the properties getters/setters
in the order they appear in the group. This means changing groups will
change the location of the getter/setter making the diff generated hard
to read.
See diff here for example: https://codereview.chromium.org/2889323002

This CL sorts fields and subgroups deterministically in alphabetical
order.

Diff: https://gist.github.com/7b50d7f151021057eded58e5a405e724/revisions

BUG=710938

Review-Url: https://codereview.chromium.org/2905803002
Cr-Commit-Position: refs/heads/master@{#474896}
1 file changed