ENH: Add view pointer to the analysis class.

In order to grab information from the view while
doing analysis, a new voView member has been added
to voAnalysis and it is set when the analysis is
created throught the analysis driver.
ENH: Add tree collapsing method.

Enable selection by collapsing the tree
in the view.
Merge branch 'DropTip'

* DropTip:
  ENH: Add tree collapsing method.
  ENH: Add view pointer to the analysis class.