add androidDatabaseImplementation option for websql

[rubensayshi]

this option has been added to the cordova sqlite plugin to fallback to an older sqlite implementation; https://github.com/litehelpers/Cordova-sqlite-storage#android-sqlite-implementation

[nolanlawson]

It pains me to keep adding hacks like this to support the SQLite Plugin.

That being said, this is a huge issue for people trying to use both libraries together, so I'm +1. Could you also add some documentation to this file to explain the new parameter to people? We should probably also explicitly recommend the "2" implementation, since "1" seems quite broken.

I would also be very happy to see a version of this PR that simply passed all the options in, or merged it into a new options object, so that we don't have to keep whitelisting options as the SQLite Plugin adds them.

[nolanlawson]

Added some documentation, fixed up the commit message, and merged as 9d1b032.

Whatever works best for our users, I guess we should do that.