Bug 1092702 - Fix logviewer angular template flicker on page load

This work fixes Bugzilla bug [1092702](https://bugzilla.mozilla.org/show_bug.cgi?id=1092702).

This adds the [ngCloak](https://docs.angularjs.org/api/ng/directive/ngCloak) directive to selected elements of the logviewer, which were flickering on page load prior to compile. I'm not sure about super fast machines but it was occurring on mine :).

The css included is boilerplate from the API reference, and I've confirmed the 'x-' is what also supports and fixes the behavior on Chrome.

Here's the before and after during page load:

![logviewerpageloadtransitioncurrent](https://cloud.githubusercontent.com/assets/3660661/4884496/5532b170-636c-11e4-9dd8-ff78a8b7143e.jpg)

![logviewerpageloadtransitionproposed](https://cloud.githubusercontent.com/assets/3660661/4884497/591808bc-636c-11e4-957a-16377763952e.jpg)

And of course here is the appearance on page load completion:

![logviewerpageloadlanding](https://cloud.githubusercontent.com/assets/3660661/4884500/6457c6d6-636c-11e4-95ad-5fad8d22895a.jpg)

Tested on Windows:
FF Release **33.0.2**
Chrome Latest Release **38.0.2125.111 m**

Adding @camd and/or @maurodoglio for review.