Lccserver

New stuff

- added `edit-collection` lcc-server CLI command.

Fixes

- fixed typo: `abs_gaiamag` should have been `gaia_absmag`. These will now be
extracted correctly from the checkplot pickles if present.

Fixes

- cli, backend: fixed operations that were actually broken, but were working
because we weren't testing them right.

Changes:

- docs: removed useless markdown version of Jupyter notebook walk-through.

Fixes

- README: use absolute links since we now use README.md at PyPi as well.

- Initial release.