Add optionnal environment entry to database

See merge request !122

This makes use of the new environment field that can be
added to the database declaration and is then used to
select the runtime environment in place of the database
search done until now.

This replaces the database name based search.

This field will allow to specify which environment should
be used to use a database. If not present, the old detection
process is used.

Fix database prototype

Closes #97

See merge request !121

This ensure that the setup call is properly done

Move to new images

See merge request !120

Add test assets with too long descriptions

See merge request !119

This will allow to improve tests also in beat/beat.cmdline>

Logger cleanup

See merge request !118

Update all logger.warn calls to logger.warning as warn is obsolete.

Also removes all unused logger instances.

Add size constraint for description field

Closes #95

See merge request !117

The max length matches the one from the database of beat/beat.web>

Don't use f string yet

See merge request !116

The processing nodes are not on Python 3.6 yet
therefore these can not be used.

The other uses are only related to tests and
tasks not done on the processing nodes.

Only enable GPU runtime if available

See merge request !115

Some execution environments may run CPU as well as GPU
code, this check for Nvidia driver presence will allow
to reuse the same environment on both.

It also updates the GPU option to use the latest version
provided by the nvidia-docker2 documentation.

Improve execution handling

See merge request !114