Improvements to plot params to:
* Raw data and LFL are optional cli arguments; if not provided GUI is presented
* Label where data is All Masked or ASCII so not drawn
* Multi-states display values mapping in legend
* Ensure single axis entries are turned into a list (no need for trailing comma)
* Log parameters plotting before kicking off
* Raise ProcessError when processing failed so program exists - normally because new lfl or data file needs to be selected.
Read percentage sections of data file (quicker)
Use cached copy of file part to speed up re-analysis
PEP8 fixes