Fixed a missing group clearing and update for restored VIEW_ITEMs.Fixed a missing group clearing and update for restored VIEW_ITEMs.

- VIEW_ITEM::ViewUpdate() does not update items immediately. Now it marks them to be updated and the real update occurs on the next rendering frame.
- VIEW::InvalidateItem() made private.
- VIEW_LAYER::enabled -> visible
- Some functions moved to header files.

Most of the GAL tools are activated by corresponding buttons on the right toolbar.
Removed menu entry for PNS router (as it is activated as the usual "Add track" tool).

New items are created using pointers (instead of copying automatic variables when drawing is finished).

Changed PCB_EDIT_FRAME::setTopLayer() to PCB_EDIT_FRAME::SetTopLayer() and changed to public (as it had exactly the same functionality).

Removed redundant fields DIMENSION::m_arrowD1O, m_arrowD2O, m_arrowG1O, m_arrowG2O (==m_crossBarO/F).
Added DIMENSION::SetOrigin(), DIMENSION::SetEnd(), DIMENSION::GetOrigin(), DIMENSION::GetEnd(), DIMENSION::GetHeight().
Fixed flipping for DIMENSION class.
Added an information that helps to understand roles of the points in the DIMENSION class.
Some minor changes to PCB_PAINTER (mainly using const COLOR4D& for taking the result of GetColor() function).

Drawing tool reacts to rotate & flip events while placing a text.

Removed an unnecessary header from class_board_item.h.