Add support to specify location and iosDatabaseLocation

[EugeniaM]

This PR contains:

• A BUGFIX

Describe the problem you have without this PR

When using 'cordova-sqlite' adapter (which uses native Cordova SQLite as its backing store) we need RxDB to create an instance of PouchDb with specified location or iosDatabaseLocation (these are required by cordoa sqlite plugin).
So an instance of PouchDb should be created like this:

new PouchDB('dbname', {adapter: 'cordova-sqlite', location: 'default'})

or this

new PouchDB('dbname', {adapter: 'cordova-sqlite', iosDatabaseLocation: 'default'})

The current implementation of RxDB let us specify only adapter.
This PR will give the possibility to specify location or iosDatabaseLocation in options property when creating database

await RxDB.create({
  name: 'dbname',
  adapter: 'cordova-sqlite',
  password: 'passwordPasswordPassword',
  options: { location: 'default' }
});

Todos

• Documentation

[pubkey]

Hi @EugeniaM
Sorry I didn't have the time to answer this weekend.

I have the fear that using the whole options-object merged into the pouchdb-settings, can cause conflicts. So wen you add something to the options for a plugin which is also recognized by pouchdb, you have a problem.

Can we change it to introduce pouchSettings in RxDatabase, like it's done in RxCollection

[EugeniaM]

@pubkey
Sure, no problem. I will change it in new commit to this PR

[EugeniaM]

@pubkey
Added new commit to #567

[pubkey]

Wow. Thank you for that awesome PR. Merged.