add pya init command to cli to init ~/MyPyaerocom path

[jgriesfeller]

Is your feature request related to a problem? Please describe.
for external usage users need to adjust the paths settings coming as default from
https://github.com/metno/pyaerocom/blob/main-dev/pyaerocom/data/paths.ini.
The path ~/MyPyaerocom is only created on the first import of pyaerocom. To make things easy for the users, it would be nice to have an easy way of speeding that up.

Describe the solution you would like to see
Intriduce a command pya init that creates the path ~/MyPyaerocom and maybe also copies the default paths.ini there