Fix comment to match code.
Fix the order of the arguments supplied to the getVar call to correctly extract the region of interest. The HYCOM OPeNDAP server is still unbelievably slow, so debugging this is tedious. Also updated the help and removed some old unneeded code.
Work around the slow HYCOM OPeNDAP server by requesting a day at a time only (or a single time step at a time). This seems to have made the speed reasonable (~5-10 minutes per variable per month).
Create a new function to interpolate the HYCOM data onto the model open boundaries.
Change the function to use a URL for each time step.

Since the 4D variables are extracted a single time step at a time, the
URL which is used to get the data can be selected for each time step.
This means that this function is now able to extract data from across
year boundaries and from multiple different URLs. This required some
fairly major changes to the way the function was organised and needed
a small child function to select the appropriate URL.

The code has also seen some clean up (in terms of only doing things once
and not bothering with preallocating arrays which don't need to be
preallocated).
Merge branch 'dev' of github.com:pwcazenave/fvcom-toolbox into dev