Baro compensate only returns records where diver was in water.
(i.e. diver noticeably greater than baro pressure)
Remove repeated spaces from keys in header.
Solves problem where "End date / time" is written "End   date / time" to align with "Start date / time".  Then, update.header() produces in "End   date / time" and "End date / time" lines.
Extended trim.out.of.water(): works for out-of-water at the end.
New parameter 'what': 'before' (default) trims at beginning, 'after' from end of dataframe; 'both' also possible.
Read MON files with electrical conductivity.
Checks header for channel names; if conductivity present, put it in column 'cond'.
Write MON file header with electrical conductivity.
format.header() will write "Channel 3" sections if necessary.