better handling of default storage directories

[joernu76]

Follow XDG convention and use may

In [1]: import xdg

In [2]: xdg.XDG_CONFIG_HOME
Out[2]: PosixPath('/home/icgXXX/.config')

In [3]: xdg.XDG_CACHE_HOME
Out[3]: PosixPath('/home/icgXXX/.cache')

In [4]: xdg.XDG_DATA_HOME
Out[4]: PosixPath('/home/icgXXX/.local/share')

for default paths.

• .config/mss is already used and correct.
• FTML files should go in ~/Documents/mss
• MSCOLAB local stuff should go to .cache/mss or .local/share/mss

[ReimarBauer]

I still want to be able to use a mss_settings.json from a nextcloud server or save images from topview by fs to a webdav system, or export to a network storage.

[joernu76]

Should not be a problem if fs handles native paths gracefully.

[ReimarBauer]

I want to use webdav urls of the pyfilesystem2 not os mounted pathes. Currently I can open a shell on my docker container and can add a fs path url so it did store outside of the container.

Any change to the current pathes needs a tutorial or/and migration script for our users.

[ReimarBauer]

This is postponed after https://open-mss.github.io/develop/GSOC/replace_pyfilesystem2