Replacement of classes BOX2 and VECTOR2 with their extended versions

include/vector2d.h: Removed old version
include/math/math_util.h: rescale() for VECTOR2
include/math/vector2d.h: New version of VECTOR2
include/math/box2.h: New version of BOX2
common/drawframe.cpp: Refactorization of code, so it is compatible with new classes
include/plot_common.h, pcbnew/basepcbframe.cpp: Changed header inclusion path
CMakeLists.txt: Added definition to turn on WX_COMPATIBILITY for replacement classes
Added template MATRIX3x3 for handling general 3x3 matrices (for future usage in GAL)
Added class COLOR4D that contains color representation with 4 components (RGBA) (for future usage in GAL)
Added template RTREE and class VIEW_RTREE (R-tree for fast spatial indexing of VIEW items; for future usage in GAL)
Introduction of Graphics Abstraction Layer based rendering for pcbnew.

New classes:
    - VIEW - represents view that is seen by user, takes care of layer ordering & visibility and how it is displayed (which location, how much zoomed, etc.)
    - VIEW_ITEM - Base class for every item that can be displayed on VIEW (the biggest change is that now it may be necessary to override ViewBBox & ViewGetLayers method for derived classes).
    - EDA_DRAW_PANEL_GAL - Inherits after EDA_DRAW_PANEL, displays VIEW output, right now it is not editable (in opposite to usual EDA_DRAW_PANEL).
    - GAL/OPENGL_GAL/CAIRO_GAL - Base Graphics Abstraction Layer class + two different flavours (Cairo is not fully supported yet), that offers methods to draw primitives using different libraries.
    - WX_VIEW_CONTROLS - Controller for VIEW, handles user events, allows zooming, panning, etc.
    - PAINTER/PCB_PAINTER - Classes that uses GAL interface to draw items (as you may have already guessed - PCB_PAINTER is a class for drawing PCB specific object, PAINTER is an abstract class). Its methods are invoked by VIEW, when an item has to be drawn. To display a new type of item - you need to implement draw(ITEM_TYPE*) method that draws it using GAL methods.
    - STROKE_FONT - Implements stroke font drawing using GAL methods.
                          
Most important changes to Kicad original code:
    * EDA_ITEM now inherits from VIEW_ITEM, which is a base class for all drawable objects.
    * EDA_DRAW_FRAME contains both usual EDA_DRAW_PANEL and new EDA_DRAW_PANEL_GAL, that can be switched anytime.
    * There are some new layers for displaying multilayer pads, vias & pads holes (these are not shown yet on the right sidebar in pcbnew)
    * Display order of layers is different than in previous versions (if you are curious - you may check m_galLayerOrder@pcbnew/basepcbframe.cpp). Preserving usual order would result in not very natural display, such as showing silkscreen texts on the bottom.
    * Introduced new hotkey (Alt+F12) and new menu option (View->Switch canvas) for switching canvas during runtime.
    * Some of classes (mostly derived from BOARD_ITEM) now includes ViewBBox & ViewGetLayers methods.
    * Removed tools/class_painter.h, as now it is extended and included in source code.
                         
Build changes:
    * GAL-based rendering option is turned on by a new compilation CMake option KICAD_GAL.
    * When compiling with CMake option KICAD_GAL=ON, GLEW and Cairo libraries are required.
    * GAL-related code is compiled into a static library (common/libgal).
    * Build with KICAD_GAL=OFF should not need any new libraries and should come out as a standard version of Kicad
                            
Currently most of items in pcbnew can be displayed using OpenGL (to be done are DIMENSIONS and MARKERS).
More details about GAL can be found in: http://www.ohwr.org/attachments/1884/view-spec.pdf
Added possibility to show/hide layers using right sidebar (PCB layer widget) in the GAL rendered view.
Showing module's value and reference text on proper layers.
Added loading layer visibility settings when loading a board. Minor code cleaning.
Added painting of DIMENSION & PCB_TARGET items. Removed unnecessary header inclusion.
common/painter.cpp: Removed unnecessary header inclusion, added variable initialization
common/view/view.cpp: Added line to comply with coding style
Added GetMinDepth()/GetMaxDepth() methods (useful for displaying things on the top or on the bottom).
Added GetSettings() method for obtaining current rendering settings used by PAINTER class.
Added missing CMakeModules (Cairo & GLEW).
Added setting active layer in PAINTER's render settings according to the PCB layer widget.
Fixed code formatting.
Fixed bug of displaying stroked rectangles on wrong layer depth.
Added high contrast display mode using GAL rendering.

New methods in VIEW class: SetTopLayer(), EnableTopLayer() for managing the top layer display.
New method in PCB_RENDER_SETTINGS class: LoadDisplayOptions() for applying display settings like high-contrast, outline display of items, etc.
Added outline display mode for pads, vias & tracks
Fixed distorted polygons' corner display
Fixed drawing of circles in certain circumstances using OpenGL.