Browse tags and their relations while filtering questions [feature/tag-browser]

# A controversial feature

## Architecture

* Collection view will hold all the tags (initially all tags ordered by occurance)
* Footer will show number of questions matching selected tags
* Header will contain search bar holding filter-phrase in text form
* The tag-browser will allow browsing a tag's relation in a n-1-only fashion as such we will not limit the relations to the whole set of pre made selections but only to the last selected one.

## Interaction

* Tags in collection view will be reloaded with new tags upon a single tap on any tag on screen
* Search bar holds tags which can be added as filter (as in questions view) by double tapping on a tag
* The footer will contain a view indicating the number of questions still matching the current filter (selected tags in conjunction), tapping will load the questions view with filter
* Navigating through the screens shall be enabled by swiping on the main view

## UI mockup

<a href="https://raw.github.com/opfo/resources/master/Mockups/Exports/Tag-Browser-View-20130506T2131.png"><img alt="The Tag-Browser" width="320px" src="https://raw.github.com/opfo/resources/master/Mockups/Exports/Tag-Browser-View-20130506T2131.png"></a>

## Tasks

- [x] Add item to tabbed-bar loading the collection view
- [x] Setup boilerplate code for collection view
- [x] Load tags as collection view cells
- [ ] ~~Size tags by occurrence, reflecting their order relatively~~
- [x] Push to navigation controller upon tap and load questions view
- [ ] ~~Enable swiping through previously made selections~~
- [x] Push to navigation controller on double tap
- [x] Setup header, showing whats displayed (common or related tags)
- [x] Show selected tags in header
- [x] Allow removal of selected tags by tap in header
- [x] Setup footer, refresh matched questions and load questions view
- [x] Do some crazy animation stuff
- [ ] ~~Reflect selections made in search bar as string in common tag-notation ([css3] [html4])~~
- [ ] ~~Get some sleep~~

That'll be all folks...