Working with generated columns

[moufmouf]

We should be able to "insert" a bean even if it has generated columns.

DBAL currently does not allow us to identify those columns so we could tag them explicitly with @generated tag.

TODO:

• Make sure we insert only modified columns (and not all columns)
• Detect @Generated tag and stop generating setter and parameters in constructor
• Test
• Document

[moufmouf]

Used @readonly instead of @generated for the annotation as this is more descriptive of what is being done.