- resetting relative coordinates
- switching units
- not official: changing transparency for layers (works only for main layers, does not work on vias/pads/etc.)

Screen size is saved in VECTOR2I instead of VECTOR2D.

Added a few settings to make the layer settings more similar to KiCad defaults (moved vias to VIA_THROUGH_VISIBLE, added a few rules for required layers).

TOOL_EVENT message is supposed to contain string as parameter.
Added missing header for class_drawsegment.h (KiROUND).
Renamed SELECTION_TOOL::containsSelected() to SELECTION_TOOL::selectionContains().

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.

Added REASON enum for Reset() function, so tools will know why a reset occured.
Fixed SELECTION_TOOL (it was bailing out, when a new board was loaded and some items were still selected).
Added removal of VIEW_ITEM groups after changing layers and removing items.

Fixes the case, when waste is never greater then the worst case and seeds assignment does not occur.

template<> -> template <>
Some more reformatting according to uncrustify results.

Added typedefs for VIEW_GROUP iterators. Fixed improper order of layer drawing for VIEW_GROUP items.

VIEW_GROUP now does not change depth during drawing. Introduced functions for manipulating stored items.
FIxed problem of overlay being covered by other layers while panning.
Few minor fixes.

Changed VIEW::PrepareTargets() to more appropriate name VIEW::ClearTargets(). Added SELECTION layer to always-on-top list.

Mouse movement events are sent during autopanning, as the cursor position changes in the world coordinates (even if it stays still in the screen coordinates). It allows tools to update their state, as if the mouse was moved.

Redraws can be requested way too often than it is required. This commit adds redraw timeout:
- if the view became dirty and there has been no redraw for longer than certain time, it is redrawed immediately
- otherwise, we wait for the next frame

This in general improves smoothness of rendering.