move ${Boost_LIBRARIES} into cvpcb, pcbnew, _pcbnew and out of github, because worker threads used regardless of github

Better GITHUB class header documentation, better eeschema library field dialog stretching and title.

   comment for GITHUB_PLUGIN which should flow into Doxygen output.
*) Rewrote: 
        PCB_BASE_FRAME::Save_Module_In_Library(): now uses fp-lib-table and PROPERTIES.  
        PCB_EDIT_FRAME::ArchiveModulesOnBoard(): now can archive to any writable library type.
        PCB_BASE_FRAME::SelectLibrary(): is now generic for selecting a library, not just the active library.

Pcbnew: add WIN32_LEAN_AND_MEAN define in github_plugin.cpp. Note: this define is already in use in avhttp build (Windows specific)

GITHUB_PLUGIN uses redirected URL to remove one HTTP hit time.

*) Move button handlers to LEFT MOUSE CLICK from COMMAND events, so wxGrid focus is not lost.
*) Sketch out the concept of COW support for the GITHUB_PLUGIN in its @todo.

* Build OpenSSL from source using the OpenSSL-CMake project on Windows with MinGW when no specifying OPENSSL_ROOT_DIR

*) Set environment variable KISYSMOD before loading FP_LIB_TABLE so that
   FP_LIB_TABLE::ROW::SetFullURI() can do substitution up front.
*) De-emphasize the lib path in some of the footprint frames but keep it
   so the footprint editor can export a current library to another.
   You can even export a GITHUB library to a pretty library for local 
   installation.
*) Start the PLUGIN options editor.
*) Enhance cursor positioning in DIALOG_FP_LIB_TABLE.

* Pre-built binaries for OpenSSL can be used from the LuaDist project: https://github.com/LuaDist/openssl/releases
* Building of Boost libraries fixed for Mingw-w64 for github plugin

Fix throwing of IO_ERROR in plugin.cpp by converting function name to wxString.GetData().
Switch to const PROPERTIES* in GITHUB PLUGIN functions.

Other platforms to follow as volunteers test support and get openssl in 
place.

BUILD_GITHUB_PLUGIN will build GITHUB_PLUGIN on Linux now.  Don't know if the parser works yet, but the FootprintEnumerate() function worked in testing.

Lay basis for a more full featured usage of boost, including compiled libraries such as unit_test_framework, system, etc.  Move headers now into boost_root/include/boost/.