Fixed properties mapping.

This fixes regression introduced in CAPX-88.
Changes to mapper form in properties section leads to data structure changes and broken import.
Fixed by restoring original data structure.

Steps to reproduce regression:
* Checkout 7.x-1.x branch
* Create a simple mapper with node page entity and title property filled
* Create an importer and run import

How to test:
* Switch to this branch
* Resave the mapper
* Run import again