command: add assets command to build statics and/or assets independently

[ppanero]

Changes:

• Adds an assets command.
• Allows collecting statics
• Allows building with webpack
• Allows both of the previous actions at the same time.

Caveats:

• The webpack buidlall part displays the full logs on the terminal. It is due to some internal part of it printing to stdout and now allowing control. It will be most likely be fixed by Enable CliRunner to echo output to stdout/stderr pallets/click#737 and/or when we manage to fix Internal Server Error because build --dev should run commands via pipenv #66 using an interpreter.
• Not implemented for --prod. Since it requires a restart of uwsgi. I assume the workflow for this would be to update statics and rebuild the app container (not base) if not. All after having tested/modified in a --dev environment. (No ?)

Closes #24

[fenekku]

Not implemented for --prod [...] workflow for this would be to update statics and rebuild the app container (not base) if not

Yes. This should be documented somewhere so it is clear: the workflow is edit your local work and run --dev. When ready generate --prod.

[ppanero]

Created issues / addressed comments.

Yes. This should be documented somewhere so it is clear: the workflow is edit your local work and run --dev. When ready generate --prod.

Agree, will start writing something (I understand that you agree with the workflow mentioned above?). Maybe we can start creating more pages in the Wiki until we have a doc tool.

[fenekku]

The workflow is good by me!