resmgr download: allow arbitrary locations

[bertsky]

Currently, our precaution of only downloading to those resource-locations which the processor supports resolving, is quite user-unfriendly:

ERROR ocrd.cli.resmgr - The selected --location {location} is not in the {this_executable}'s resource search path, refusing to install to invalid location

In my case, the module directory is /usr/share/tesseract-ocr/4.00/tessdata/frak2021.traineddata (from Tesseract deb), which is not writable for normal users (but sudo would need the venv).

As a user I should be allowed to override --location regardless. At least -l cwd should always be possible.

So can we downgrade the error to a warning?