Added missing files to setup.py

If I install Printrun via setup.py, I don't have gcoder.py and I cannot even
use pronterface.py:

Traceback (most recent call last):
  File "/bin/pronterface.py", line 46, in <module>
    import pronsole
  File "/usr/bin/pronsole.py", line 23, in <module>
    from gcoder import GCode

So I've added this to setup.py.

Also, pronsole.ico is missing, added that to (not needed at runtime, but is
usefull for desktop files)
Making the whole package GNU GPLv3+.
Merge pull request #300 from hroncok/master

Added missing files to setup.py and fixed license notice in files which were not explicitly gplv3+.
Bugfix: printcore.py -s was generating garbage output
gcoder.py reads only hte content of the file
Previously, gcoder.py read not only the content of the file, but also it's
filename. This could have led to unexpected exceptions.
Merge pull request #316 from hroncok/master

gcoder.py reads the file content instead of the file name when testing
Tell the user, there was an error while connecting

Before, when there was an error while connecting, user didn't know, when
Pronterface wasn't launched from the terminal.

So you could just hit Connect button several times and all you've get was:
Connecting...
Connecting...
Connecting...

Now, when there is an exception during the connection, the user will notice:
Connecting...
Error: You are trying to connect to a non-exisiting port.

Or:
Connecting...
Error: You don't have permission to open /dev/ttyUSB0.
You might need to add yourself to the dialout group.

Unfortunately pyserial's SerialException doesn't provide errno yet, so the
message isn't so user friendly:
Connecting...
could not open port None: [Errno 2] No such file or directory: 'None'

I've filled a bug report with patch to pyserial.

Together with this I've realised, there is unnecessary UTF8 decoding of the
output. When user has UTF-8 locale, there was an exception when printing the
exception to the output (almost an exception inception). So I have dropped it,
but feel free to add it back, if I broke anything else.
Adding UTF-8 decoding back
Handle UTF encoding better
Do not rise, but end the scope
Merge pull request #318 from hroncok/master

Show connection error to the user
Merge branch 'master' of github.com:kliment/Printrun into experimental

Conflicts:
	gcoder.py