Introduced SELECTION_CONDITIONS to determine which menu entries should be visible in the SELECTION_TOOL context menu, depending on the selection.

Reworked the way of processing events in TOOL_MANAGER class.
Added GetCommandStr() for TOOL_EVENT class.

Introduced a new type of action: TA_ACTIVATE to distinguish events activating tools from common tool actions.

Reduced number of switched events, allowing to use VIEW_CONTROLS, even if there is no extra event dispatcher.

Event handlers are (dis)connected depending on the active view.
TOOL_DISPATCHER inherits from wxEvtHandler, so now it receives events directly instead of being fed by external handlers.

Moved menuCopy to CONTEXT_MENU copy constructor.

Resolved HOME hot key conflict between menu entry (Zoom Page) and event assigned to the hot key in the ACTION_MANAGER.
Conflicts:
	pcbnew/menubar_pcbframe.cpp

Key events are handled by wxEVT_CHAR instead of wxEVT_KEY_[UP|DOWN]. Fixed issue of chars that require modifiers (e.g. ? is Shift+/ on US keyboard layout).

Hot keys specific to a tool have priority over global hot keys (TOOL_ACTION scope: AS_GLOBAL/AS_CONTEXT is finally handled properly).

Renamed [class_]drawpanel_gal.[cpp|h] to [class_]draw_panel_gal.[cpp|h] to follow current naming scheme.

If tool was previously active and it is called again, it is brought to the top of the active tool stack.
It fixes issue of dragging of items that have EDIT_POINTs, when dragging was activated by hovering over an item and using hot key.

Refactored code that handled zooming events.
Added PCB_RENDER_SETTINGS::Get/SetSketchMode().
PCBNEW_CONTROL reacts to hot keys changing display modes (sketch via/tracks, high contrast).