Build polygon from intersection of other shapes (for filling) (lp:#1812946)

Original report created by zakhar nasimov (thedocument)

It would be ideal to permit users to shade a region of closed contours
permitting shapes to be solid entities on the layer which the user prefers
to have them in. This should work for any closed contour of residing on the
same layer including the copper layers.

Application: kicad
Version: 5.0.1, release build
Libraries:
    wxWidgets 3.0.4
Platform: Linux 4.19.7-gentoo x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 2.24
    Boost: 1.65.0
    OpenCASCADE Community Edition: 6.9.1
    Compiler: GCC 7.3.0 with C++ ABI 1011

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=OFF
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=OFF
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=OFF