Added folder monitoring capability and fixed emulator launching problem.

- The folder monitoring allows users to add one or more native android
apps on fly and selendroid immediately signs and adds these files to
the app store so they can be used without restarting the node.
- Adding one seconds wait before calling "isDeviceReady" to avoid the
command sent too quickly while the emulator still starting and not ready
to receive any commands

Signed-off-by: Binh Vu <bvu@paypal.com>
No, since the supportedApps just a space holder for all apps that need to be added to the app store before the node started. After starting the node, it is disposable. The FolderMonitor will add all apps in the folder directly to the app store. I don't see the need for getSupportedApps other than for backward compatibility, or for users who don't want to use FolderMonitor.