Feature: Open more that one file

Used a TabWidget to control the open/close of gcode files.
Using KTextEditor as base, you need one Editor, and a view
for each document. So the newView and newDoc methods works for
this.
Added a signal to change the guiFactory view related to the
files edited.
Tried to make a nicer way to the helpers of the factory appears
however the program is crashing. The code related is comment
for further review.

Signed-off-by: Lays Rodrigues <laysrodriguessilva@gmail.com>