Arch: Added Equipment tool

The purpose of this tool is to handle standalone objects such as
furniture or sanitary equipment in a building. It is mesh-based,
and accepts either a mesh or a part shape as its base object.
+ allow to load PartDesign even if PySide is not found, suppress MinGW warnings
Arch: allow for equipment objects to be part shapes
+ fixes #0001719: Show current shortcuts (S) in menus and hover text.
+ do not abort if user.cfg or system.cfg is empty
Arch: fixed bug in importIFC
Plot: Fixed PyQt imported in the resources loading
Arch: fixed import IFC again (better this time)
Added Gui.showDownloads() py function to show the download manager, and allow to click https links in webgui browser
Arch: optimizations in IFC import + furniture objects can be included in spaces
python property Continuity of GeometrySurface
exportDRAWEXE: support Part::Plane and ::Ellipse
+ fixes #0001714: FreeCAD 0.14 Stable crashes when importing a step model
issue #1700 replace raise Exception()
fixes #0001422: Subclass Exception

inherit Base.FreeCADError form RuntimeError
inherit Part.OCCError from Base.FreeCADError
Added PY_CATCH_OCC macro
replace PyExc_Exception
use FreeCADError in makeWireString
removed catch (...) in Drawing

which discarded type information when rethrowing base type
issue #1700 replace PyExc_Exception