MWEB-667

**DO NOT MERGE -- MOBILE WEB TEAM WILL CR AND QA IT FIRST**

* bunch of unit tests for existing PHP entry points,
* moved some existing logic from one place to another,
* added new `WikiaInteractiveMapsPermissionException`,
* implemented logic which disallows blocked user to create/delete/change maps.
Ask the author of the code ;) @bkoval, explain yourself, please :japanese_ogre:
https://github.com/Wikia/app/commit/758fe1e1e5a30a84e1892d51d22041370001acc1#diff-fccd2f80538db257e8bced9b3e5098abR454
Do you mind if I change it to `getInt()` 'cause I agree with @rogatty?