Support for multiple filters in db-djv-pg export command

[Denis Stepanov]

Currently we have:

(advent-pyenv) $ db-djv-pg export *C8* *FRANCE2*
usage: db-djv-pg [-h] COMMAND ...
db-djv-pg: error: unrecognized arguments: *FRANCE2*
(advent-pyenv) $

This is sort of intentional, but it would be more convenient if multiple such parameters could be specified.

[Denis Stepanov]

Same for delete command.