Minor change: Eeschema+Pcbnew: display timestamp in edit dialogs (for footprints, sheets, components)

* Make GPCB_PLUGIN::EnumerateFootprints() read the directory contents
  instead of loading the entire cache.
* Make KICAD_PLUGIN::EnumerateFootprints() read the directory contents
  instead of loading the entire cache.

* Make GPCB_PLUGIN::EnumerateFootprints() read the directory contents
  instead of loading the entire cache.
* Make KICAD_PLUGIN::EnumerateFootprints() read the directory contents
  instead of loading the entire cache.

kicad-install.sh and library-repos-install.sh utilize /etc/profile.d/kicad.sh for setting environment variables globally

* Prevent cache from being reloaded on every footprint file read.
* Fix a bug forming wxFileName in GPCB_FP_CACHE::Load().
* Fix invalid file name time stamp debug assertion.
* Use FPID to set loaded footprint name.
* Remove file name <> from exception strings per UIPolicy.

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

   To use multiple working threads.  This entailed adding KiCad typedefs:
*) Add typedefs for MUTEX and MUTLOCK which mask the actual choices for the project.
*) Add FOOTPRINT_LIST::DisplayErrors( wxWindow* ) which is a single strategy for
   showing aggregated load errors.  Although what's there is only scaffolding
   and needs a volunteer who knows HTML pretty well.
*) Ensure all callers of ReadFootprintFiles() use the new DisplayErrors() function.   
*) Push utf8.cpp and utf8.h into common library for open use.

Documentation/guidelines/UIpolicies.txt should not speak of the unspeakable use of <> in quoted strings.

eeschema/dialogs/dialog_lib_new_component.cpp was not expanding part name field nor setting initial focus.

* Make the tool bar dockable.
* Enable the overflow control in the tool bar in case the it does not fit in
  it's parent window.
* Fix some wxAuiPaneInfo usage issues.
* Remove unused wxAuiPaneInfo objects.
* Move perspective saving and loading into EDA_BASE_FRAME object in preparation
  for extending this to all frame windows.

Plot functions: some enhancements in mirror mode (Pcbnew specific): boards are mirrored horizontally, and the page layout is no more mirrored, and therefore is always readable.