Ported most Python 2 to Python 3 (#725)

* Fix #720, ported most python to python 3
Compatibility with python 2 was retained by adding the
`from __future__ import print_function`
statement when needed.
Changed
`except Exception, ex:`
to
`except Exception as ex:`
Changed some occurrencies of
`raise Exception "message"`
to
`raise Exception("message")`
There are many, many python scripts and I probably missed some of them. I guess I will fix them whenever an error pops up

* Fix #720, found some other python files

* Fix #720, fixed calibrationtoolclient indentation issues

* Fix #720, fixed some issues with discosConsole interfaces

* Fix #720, meteoClient updated

It now uses the Qwt python wrapper found here
https://github.com/GauiStori/PyQt-Qwt
The code has been refactored in order to be properly organized and it has been updated in order to use Qwt 6
It seems to be working properly when used in conjunction with the simulators

* Fix #720, updated meteoClient

* Fix #720, updated CaltoolClient

* Fix #720, fixed some Python 3 related errors