Python examples using directly magnum

[c-joly]

Hi @costashatz , here is an issue linked to the JOSS review openjournals/joss-reviews#6771

Some python examples are directly importing the module magnum (e.g. sensors_tutorial.py). However, the bindings of magnum are not installed by the scripts (both Linux and MacOS). Should we consider these examples as depreciated? If not, can you please update the install scripts to compile and install the bindings of magnum?

[costashatz]

@c-joly feel free to re-open the issue if #217 did not fix this :) Thanks again!