Placeholders for UI components and first implementation of UIFactory

https://wikia-inc.atlassian.net/browse/DAR-719

* added placeholders for UI components in /resources/wikia/ui_components/,
* added README.md,
* added first iteration of UIFactory (more unit tests and caching layer will be added during work on DAR-809),
* added some helpers method which will get deleted after changes in GlobalHeader.