20130122 ExtLwProcess Update

ExtLwProcess occasionally crashed due to communcation errors with magnet movers epics db, although there should be provision for this and it should continue. It was found there were a few errors in the code and also as this code was one of the first pieces of laser-wire code to be written was quite slow and done in a poor way. This was updated, tidied up and errors removed. Particular effort was made to group epics gets and puts together as the python methods take approximately the same time to get one variable as a list of about 100 variables for example, and similarly for caput.

The time per loop was recorded for 1000 loops. The mean was 46.2 +- 0.3ms. The maximum time was 217.0ms and the minimum time was 33.3ms. Even in the longest instance this is faster than the repetition rate of the machine (currently 3.12Hz). Additionally, the recorded laser-wire data does not depend on any of the variables calculated in ExtLwProcess.py and only contains raw data. The processed data is purely for display / EDM purposes.