Set preferences

[gthompson]

From @CelsoReyes on August 1, 2015 22:34

Move or create preferences for appropriate values. Implement using getpref / setpref Related to Issue #37

Note: as tested, getpref('WaveformSuite','UseHistory') has a 0.002s overhead.

Copied from original issue: giseislab/gismotools#38

[gthompson]

From @CelsoReyes on August 13, 2015 14:19

The above note looks like a small amount, but adds up quickly depending on where it is used. I've opted not to include "UseHistory" as a preference at all, since the history was ripped out of most of waveform.

implementing getpref / setpref:

• In order to reduce overhead, it can be wrapped in a class that reads the preference into a Const variable. This way the value only read once, and is always available, though it will be unchangable during the session. better when access is required everyhere and value won't change
• Another option is to read the value into a persistent variable. better for when access is limited to an individual and often-called function or class and when value might change

[gthompson]

NOt obvious to me why this is important. So closing it.