Fix minor bug in eeschema (opening a relative path does not work) (patch from HennerZeller).

Fix a minor error in class D_PAD: void D_PAD::Flip( int Y ) changed to virtual void D_PAD::Flip( const wxPoint& aCentre ) (as defined in BOARD_ITEM)
Scripting: fix compatibility current pcbnew version in 2 examples and the default extension of board files  in board.i (was .kicad_brd, now is .kicad_pcb)

gr_basic.cpp: rewrite the function which draws the outlines of a thick segment.

  Factored out the next-pad-number function

Add a workaround to fix a new bug in wxWidgets 3.0 ( Windows specific ) which shows icons only with a size = 16x16 in menus which have attribute wxITEM_CHECK

Fix some incorrect icons (which were using a not supported font for texts). Add ps_router icon from Konstantin Baranovskiy.

Moved netnames (GAL specific layers) to a separate enum, to avoid saving/reading their settings from files.
Added a check for the number of PCB_VISIBLE elements.
Worksheet & general purpose overlay layers are visible by default.

Changed BOARD_DESIGN_SETTINGS::m_VisibleElements from int to long, to assure at least 32 bits length (without depending on the platfrom int size).

Add missing calls to Show( false ) to some main frames (Kicad, eeschema, gerbview), to force config saving when closing these windows.
Code cleanup and minor coding style fixes  in footprint_wizard_frame

Add EDA_BASE_FRAME::Show() and call SaveSettings() only from there for all derived wxFrames.  Remove calls to SaveSettings() elsewhere.