Implement sane behavior of space key in torrent content list. Closes #140.

Definitions:

Selection in QTreeView consist of two things:

   currentIndex -- is a (dotted) cell where user clicked last time. Note
                   that it is a cell
   selectedIndexes -- is a set of cells (blue) of current selection.

Checkboxes in torrent content lists are belong to COL_NAME column.

Problem:

The problem is that spacebar toggled checkbox only in currentIndex
index. This has two consequences:

  1. It is impossible to toggle checkboxes on multiple rows
     simultaneously.
  2. If currentIndex is not in COL_NAME column a space key doesn't work
     at all. This problem is amplifyed by the fact that SelectionBehavior
     is set to SelectRows. So visually it is impossible to tell which
     column does it belong to. For end user it looks like "space doesn't
     work sometimes".

This patch addresses the problem by implementing TorrentContentTreeView
derived from QTreeView and overridding keyPressEvent(QKeyEvent*).

The code of TorrentContentTreeView::keyPressEvent is written under
inspiration from QAbstractItemView::keyPressEvent and
QItemDelegate::editorEvent.
Merge pull request #2172 from sorokin/fix-space-key

Implement sane behavior of space key in torrent content list. Closes #140.
saving torrent list view when changed

bc its otherwise forgotten by an unclean exit
Merge pull request #2290 from john-peterson/save

saving torrent list view when changed
Remove vertor engine. Closes #2260.

Reason: tracker is closed and redirect to TorrentReactor
Merge pull request #2291 from DoumanAsh/vertor_remove

Remove vertor engine. Closes #2260.