Added edit/delete/disable buttons to script list

Hi, I'm exploring the possibility to integrate your library into:
        https://github.com/WaniKani/Android-Notification
which is released according to GPLv3 (hope that's ok for you). 

First of all thanks for sharing your code; I had to change some classes, to ease the integration with the app:
- Added a few buttons to the script list, to perform simple management tasks
- Added a few more hooks to WebViewGmImpl, in order to keep most code, but instantiate personalized classes
- Added possibility to choose not to start the integrated browser when WebViewGmImpl is started
- Added "isEnabled" method to ScriptStore function (I believe this is the only change that can possibly break existing code, in case it has been directly implemented without subclassing ScriptStoreSQLite)
I think I'll need the @require and @resource tags. If you have already an idea on how to implement them, let me know: if I have some spare time I may try and add them. I was thinking of a separate SQL table referenced by the scripts table (may need a join table too).

Cheers.
Alberto.