Introduces ProviderBase for Markers.

Moves all provider's files to Providers namespace to get better separation and cleaner interface.
Repairs multicity chargers not displayed in WP8.

dbrent seems to deliver crappy json. The WP8-libraries are a little bit stricter than the former ones used in WP7. So they fail to encode the json-file to objects.

We replace some characters known to cause problems to solve the issue. Hopefully this will be of longer use.
Code cleanup