Blender Git Loki

Outliner: Use outliner_item_select for activation

Use outliner_item_select for outliner activation. This is used in a few
places so far and could easily be extended to other operators.

outliner_item_select takes 3 booleans, select, activate, and extend and
properly sets the TSE_SELECTED and TSE_ACTIVE flags based on the bools.

Future commits will move other selection and activation logic to be in
this function.

No functional changes. Separate the mode toggling logic from the
item activation code because these are distinct behaviors. This will
make later changes easier to make, and also makes it possible to
activate on walk select without toggling modes.

Also rename functions to make purpose more clear.