Drop Python2 support.

Starting from beginning of 2020 Python 2.7 is no longer supported[1],
hence the change of shebang for uc1541 script and removal of _ord
function.

[1] https://devguide.python.org/versions/

Code cleanup.

Clean up the code.

There was an issue regarding c1541 in old version - during removal of
the file from the image, as a success message 'ERRORCODE 1' was placed
on the stdout. If there was an issue with the file different message was
placed also on stdout. Luckily, that weird behaviour was fixed in 3.x
series of the Vice. So now we can remove unnecessary code.

Also, fixed two bugs for pyton3, introduced during new formats
development.

Changed shebang back to python.

In modern linux distributions, executable "python" is a symlink to the
selected Python interpreter. There could be multiple versions installed
on the system, and appropriate tools on certain distributions exists for
selecting default one. There is no need for changing it to explicitly
"python3" executable.

Not provided subcommand is fatal on Python3.

Added initial Python3 support

Added urls for sourcecode

Gzip support

Added mkdir and run handling (or rather lack of handling :). Minor re…

…factoring.

Fixed bug with filenames started with a '-' sign.