(bug 63616) incorrect topic timestamp

Normal request block rendering was already checking if a specific block can
be rendered ('discussion' has 3 blocks).
This was not yet the case for API requests. As a result, *all* blocks' render()
methods were called: HeaderBlock, TopicListBlock & BoardHistoryBlock, even if
the requested action is unrelated.

Basically, when API request for action=view was done, BoardHistoryBlock would
also render, even though it only supports action 'history'.
This patch will drastically cut down DB & cache requests, because all history
will no longer be fetched per API request.

It appeared that loading all history at once resulted in faulty workflow
timestamps being saved to cache, somehow. This is now no longer the case since
API calls will no longer call said history render code. I will now look into
why that was saving bad data in the first place ;)

Bug: 63616
Bug: 63346
Change-Id: I866fe0616bd8784932e314390bb2e42010bd79de