Compute the max of all total lengths

The computed duration is no more pessimistic, for a few reasons.
- the main one is that it does not take retraction into account
- Z moves are not taken into account either
- arcs are not supported
- the acceleration code seems to estimate acceleration time correctly but is
  wrong for deceleration
So instead of telling the user this estimation is pessimistic, let's just tell
them this is an estimate.

I'm hunting unjustified try: except: blocks.

The icon was adapted from the 24x24 "Refresh" icon from Humanity Icon theme.

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.