[Qgis-developer] [WIP] Coordinate formatter class + registry for plugin based coordinate formatters

[Nyall Dawson]

Announcing work in progress regarding pulling the coordinate
formatting methods out of QgsPoint into a more flexible coordinate
formatter class.

An initial prototype is available here
https://github.com/qgis/QGIS/pull/2586, but based on feedback from
that PR I intend to extend the work and create a registry of
coordinate formatters so that plugins can provide custom formatters
(eg specific local coordinate formats).

The work is NOT definite yet, but I'll be continuing to hack on it
while I have spare time.

Nyall