add select_all function

[dant4z]

I tried to create universal select function with grouping, ordering and where conditionning

[leafo]

Thanks for the patch. I'm thinking this functionality should be part of Model\select.

Currently select takes a string as a first argument and interpolates that as a query. I think a good API would be to let it also take a table that follows the rules you created here.

[lordnynex]

Bump. I would benefit greatly from this functionality being added into Model\select.

[leafo]

Closing outdated pull request. Going forward I recommend using db.clause inside of query interpolation.