Lots of updates.

# Groundhog 0.5

- The “show/hide” tools were moved from the Groundhog Toolbar to the
View menu.
- The “Show Window Groups” tool was algo moved to the View Menu.
- It is now possible to export a model without saving it as well as
saving it in a different directory.
- The “Add Workplane” tool was downgraded to a simple script. It is
more comfortable since the user no longer has to write down the height
of the Worplane. The Workplanes may be moved just as any other face.
- Added the “Label as workplane” Context Menu. The faces have to be
horizontal.
- Window Groups and Workplanes require a name. This name will be used
for exporting them.
- Components may now be exported. Even Nested components (components
within components) seem to be working OK. Groups are trickier.
Merge branch 'NestedGroups' into HEAD-version