Fix sending mixed delete/insert text commands for WebOSService.

Change kKeyboardEnter/kKeyboardDelete to strings that are unlikely
to conflict with legitimate input.
Merge pull request #18 from jlai/sdk_1.2-dev

Fix sending mixed delete/insert text commands for WebOSService.
Added convenience method joinWebAppWithId
Merge remote-tracking branch 'origin/sdk_1.2' into sdk_1.2-dev