Improve the RTL support of the System app by refactoring the stylesheets for these building blocks: • date_selector • time_selector • value_selector

Hey Pavel, :-) most of this patch should be a straight-forward CSS refactoring, to match our BiDi guidelines [1]. Main points worth noticing: • time_selector, there was a typo in the `12hrev` format that had to be fixed in a couple JS files (trivial fix); • date_selector, I’ve had to redo a rather big part of the stylesheet. The date and time selectors aren’t just about mirroring rules from LTR to RTL, as some parts remain at the same position whatever the language direction is.

Ooops, I posted this patch with the wrong bugzilla account. Sorry.

I left few comments in github ... but everything else looks good :) thanks r+

Comments addressed, commits squashed. Thanks Pavel! :)

Kazé, Are we waiting for bug 1207131 to land this and similar bugs that have non-green tests?

Merged on master: https://github.com/mozilla-b2g/gaia/commit/405c72c