ArrayMap class

This pull request implements xp-framework/rfc#184 and adds the `lang.types.ArrayMap` class.

* [x] Add ArrayMap class to lang.types
* [x] Deprecate util.Hashmap 
* [x] Rewrite util.Properties: Deprecate readHash() / writeHash(); add readMap(), writeMap() instead
* [x] Refactor unittest.mock package to use util.collections.HashTable instead of util.Hashmap
* [x] Apply boyscout principle and clean up codebase a bit