Deployment Metadata Selection

Improved UX for metadata selection on deployment.
* Don't clear the search filter when starting a new search (useful when the wrong meta type is searched)
* Clear search when search filter is changed (prevents having to click to reset)
* Clear search search when meta type is changed (prevents click to reset)
* Add icon for select/deselect all, fixes https://github.com/joeferraro/MavensMate/issues/47