Okai, this may not make that much sense. However when removing the mainloop,
pronterface was segfaulting when Python was freeing everything. As a
workaround, explictely destroy the wx application, which will cleanly free
things in order, while Python might destroy wx things in a random order.

Conflicts:
	printrun/gviz.py

As far as I understand, a wxFrame needs a wxPanel child, but we shouldn't
reparent this wxPanel to some other container. As a consequence, I created an
initial wxPanel for the gwindow wxFrame and assigned it the previous sizer
(instead of using the gviz panel as the wxFrame's panel).
Not sure why it wasn't segfaulting on my other systems, though.

Not sure about that dropping of the self.gwindow.Destroy try block, we'll see

The gauges options is a CLI parameter as having it as an option would be
too painful to handle for now.
Argument parsing has been improved so that pronterface can add its own CLI
parameters in addition to pronsole's ones.

Should fix #348

This reverts commit 02ef52d7.
First step towards getting the gauges optionally back for #296.

This should fix the weird graph background for #359

One of the strings is to give a hint for wrong baudrates (#276)

Should fix #359 initial issues

Conflicts:
	.gitignore
	printrun/gui.py

There is a lot of code duplication between addgcode() and add_parsed_gcode,
which would probably need to be cleaned up.

This might be slightly off, but it could also be the zooming code that's off.

This commit mostly removes unused code and cleans some things up.
The main contribution is that instead of calling repaint() and Refresh(), we
now only mark the canvas as dirty and call Refresh(), which will do the repaint
just-in-time. This speeds things a lot when quickly changing layers or zooming,
as it does not repaint once per keyboard/mouse event but once per actual
Refresh, which makes it much smoother.

FWIW, on my test system with my test GCode loading time goes down from 5.7s to
2.3s between b3a673bc and this commit, that's almost 60% gone.
However, there is still a lot of room for functional improvements :
- I don't think the roundtrip through the target array is useful
- There's no handling of relative coordinates (neither for position nor for e)
- The arcs drawing code might be wrong
- The stlview bits are not enabled and probably have to be looked at and updated

Command line option parsing really needs a better rework, to use optparse or
argparse and support gcode/stl filename argument.