Allow offical plugins to be searched on mobile app

[IamTechknow]

This corresponds to #1228 which suggest making plugins searchable, to be turned on or off more quickly. Here is my implementation, it involves populating a SQLite database which is queried whenever a user types in the search view. It shows the names of all plugins that start with the query which are search suggestions. When a suggestion is tapped, the plugin is toggled as if it's checkbox was clicked and a Toast notifies the user.

The search widget shouldn't interfere with the add script feature already in place. It turns out the activity is not launched in singleTop mode so a new activity is created to handle the search, but I handle the suggestion in onCreate() and then call finish() so the activity animation doesn't occur and there are no other side effects. I made changes to PluginPreferenceActivity.java, some are changes to existing methods while others are new methods.

[IamTechknow]

Closing this now because there's no activity for a long time and the need for this is questionable. I remember creating this PR to see if this was possible

[johnd0e]

@IamTechknow

In fact this is really needed feature, and there is activity in modern fork - iitc-ce.
Feel free to post PR there, we will be happy to include that functionality.