Allow users to sort on a specific language, showing it before any otherst a

Problem/Motivation

Some times a situation comes up where we want to show one language before any others (such as the language of the current node).

Proposed resolution

Add a sort handler, so we can sort on a specific language before any others, as described in https://stackoverflow.com/questions/14104055/ordering-by-specific-field-...

we do ORDER BY name = 'core' DESC, which works in PostgreSQL & MySQL

Remaining tasks

Review patch

User interface changes

Screenshots:

API changes

N/A

Data model changes

N/A