Python path config value

[danwos]

For needls installation we need to know the python env quite early.

This is problematic in VS-Code, as it self references different python locations:

• During startup: It's often the system-wide installed
• Then during loading of the Python Extension, is may be the just found .venv.
• After loading it may be a hard-coded / configured venv by the user.

So there is a high risk, that needls gets installed in the wrong venv is later not available.

Solution

Provide a setting, which asks for the correct Python path.
If not set, it shall be detected automatically and set as values.
If the value is set, then Open-Needs IDE is always using this value.

It shall support {$workspacefolder}.