CB-7429, CB-7440 Media-capture plugin is not working on WP8.1 since native API change

This fixes https://issues.apache.org/jira/browse/CB-7429 and https://issues.apache.org/jira/browse/CB-7440

* Adds custom UI for WP8.1
* capture* methods now resolved with proper MediaFile object
* files are captured to Appdata/local folder