Clean up divelist dive selection

Since we have a "selectDive()" method, let's just use it rather than
opencoding it.  Similarly for "unselectDives()".

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Add context menu to dive list

So far we support "expand all" and "collapse" all. This still needs to
be restricted to only be shown when in trip / tree mode.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>