ADD methods to apidoc

[AntonioCarta]

We would like to have methods documented in the apidoc. The main roadblock right now is that the doc building is killed due to excessive time/memory consumption.

See #1059

[lrzpellegrini]

I just tested adding the -j auto option in the docs Makefile as follows:

SPHINXOPTS    = -j auto

This greatly speeds up things! I may try adding a new commit to #1059 and see if it works...

[AndreaCossu]

nice, fingers crossed then!

[AntonioCarta]

closing this since it ended up being too slow for rtd