Conflict between farad and Faraday identified in quantities <0.7

Written for python-quantities by Darren Dale on 2009-12-11

F is commonly used as a symbol for both the farad and Faraday's constant. This is problematic for quanitities, which registers its units so they can be accessed using a string corresponding to the unit name or symbol. In this case, the Faraday constant was registered after the farad, so any quantity that was expressed in terms of farads would be incorrectly simplified using the Faraday constant.

This problem has been fixed in the trunk, and the registry has been improved to prevent overwriting previously registered names or symbols. F is now reserved for the farad. This problem has accelerated the schedule for releasing quantities-0.7.0, it should be available by 2009-12-13.