Removed an unnecessary header from class_board_item.h.

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.

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

Added Init() to TOOL_INTERACTIVE, allowing to set up things that are needed to be initialized only once.
TOOL_ACTIONs can be run from CONTEXT_MENU after adding them.
Move tool actions are available to be run from CONTEXT_MENU displayed after right mouse button click on selected items.
Added some asserts to check the code.

Less objects are allocated dynamically.
CONTEXT_MENU is being run using its copy (it saves a hassle of following the lifetime of object).

FIxed TOOL_EVENT::Modifier() (now it returns value for current modifier, not only if there is one active or not).

Removed TA_ActivateTool (now tools are invoked by sending TA_Action event, with the tool name as string parameter).
Developed TOOL_Action class & added ActionManager. Hot keys registered by tools are processed.
Selection & move tool can be invoked by a hot key.

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.