Add function to reverse Seaglider pressure-to-depth conversion.

Seaglider gliders do not report direct readings of pressure, but
approximate depth values computed using a constant conversion factor.
Function `sgdepth2pres` reverses that conversion.
Add function to calibrate CT sails mounted on Seaglider gliders.

Seaglider gliders report conductivity and temperature measurements
as frequency readings which should be converted to engineering units
using the equations and coefficients provided in Seabird calibration
sheets.

Function `calibrateSBECT` performs this conversion.
Add function to calibrate count data from WET Labs optic sensors.

Data from the optic sensors by WET Labs like the ECO Triplet Puck
mounted on Seaglider gliders are reported in counts.
They may be converted to engineering units by applying linear equations
with the coefficients provided in the calibration data sheets.

Function `calibrateWLECOBBFl2` performs this conversion.
Add pressure conversion function.

Pressure is used in decibars but some sensors repors it in bars.
Even though the conversion is simply a factor of 10,
it is convenient to provide a named function `bar2dbar`
to perform it when needed.
Extend nmea conversion function to support pairs of arguments.
Switch arguments of Seaglider GPS timestamp filling function.
Removed spurious second argument of Seaglider pressure conversion.
Renamed parameters WetLABS Triplet calibration function.
Cosmetic changes to Seabird CT calibration function.
Add function to align parameter values in Seaglider log files.
Add function to convert Seaglider water velocity estimates to east and north components.
Improve profile finding function with option to join consecutive casts with the same direction.
Improved sequence filling function with support for reference sequences.
Improved and renamed data base fetching function.
Renamed and updated example data base query configuration functions.
Refactor main processing functions according to new outline.

Refactor variable selection and unit conversion, and move them
to preprocessing function. Add factory calibration there.
Also add processing metadata to each processing stage.
The new outline is described below.

Preprocessing stage deals with all operations that do
not imply a change of the nominal value of a measurement:

  - variable selection
  - unit conversion
  - factory calibration
  - data record alignment

In the processing stage, apply corrections to measured
variables, possibly with parameters estimated automatically,
and derive new ones. Namely:

  - interpolate coordinate variables if needed
  - compute profile and transect index
  - compute other navigation data
  - process CTD data

In the processing stage, data is gridded over vertical profiles,
as before.
Adapt scripts and configuration to fully support Slocum and Seaglider processing.

Provide separate configuration functions for Slocum (G1 and G2) and
Seaglider data processing, and adapt main scripts to new processing
outline.