Write importer for NMEA dataset

[IanMayo]

Here is an example of a dataset where it can take several rows to build up one line of import data:
https://github.com/debrief/debrief/blob/develop/org.mwc.debrief.lite/data/tracks/NMEA_TRIAL.log

We'll need Ian to document the content first though

Actually, we could do with a different type of highlight for this data. Where data comes from several lines, it would be good if the lines for each "imported element" were shown in the same color.

So, if "State_1" came from rows 6,7,9 then they would have one color. Then if "State_2" came from 14,16,19 then they would have another color.

We don't need a different highlighter, we can just used "ToolName"+"State1" as the ToolField hash.