Implemented JSON-based html tables support for Rekall output.

More details:
* Implemented "fast-repeat" AngularJS directive to render large datasets efficiently.
* Implemented "render_sample" rekall command to produce samples of rendering output. Using this to generate json renderer output samples for tests.
* Using JsonRenderer when executing rekall plugins from WebConsole UI.
* Implemented JsonRenderer service that decodes Rekall JSON output into a meaningful data structure (javascript version of JsonDecoder, essentially).
* Have set up karma javascript tests.

Minor bugfixes:
* Added javascript-specific runtime folders to .gitignore.
* Fixed move node up/down buttons behavior.
* Fixed CertScanner to work with JsonRenderer

BUG=
R=scudette@gmail.com

Review URL: https://codereview.appspot.com/110020051