Data source doc update

[Casperhr]

Lacking data source documentation
I am missing a section in the official docs regarding data sources. Persisting data is an integral part of most web based systems and there should be a dedicated section for this to make vapor more accessible to newcomers.
Also docs regarding column attributes in my data source. Nullable fields, unsigned integers etc.
Missing docblocks in the source
One of the best things about Laravel is that most of the code base is fully documented with doc blocks. They even have design guides to how doc blocks should look. Some parts of the code base is missing this (though I have also encountered several helpful ones)
Basic database operations
Database operations are not documented with clear examples. Common operations such as UPDATE and DELETE are not present in the docs. Only a very simple CREATE along with some generic JOIN example could be found.

[steffendsommer]

Have you been working on this @rasmusebbesen or can I unassign you?