[iOS] Hyperlinking dates tab events with corresponding course content #195

As a learner, I should be able to navigate to a linked course content from the dates tab.

On back button press, the learner should be directed to the dates screen (we will be replicating the current prod app behaviour).

Previous implementation logic as per this spec.

Hyperlinking logic for a Date Block

If a Date block is:

1. for an assignment
2. that has been released
3. and the learner has access to it

then apply a hyperlink to the specified linking text in the Date block’s title.