[Proj] Intro and new Excel wrapper for proj.4

[John Buonagurio]

Hi all, 

I'm new to the list. I just finished an Excel API wrapper for 
pj_transform(), which was surprisingly straightforward thanks to the 
easy build with NMAKE and simple API (I can't say enough good things 
about this library). Here's the GitHub page with some basic 
documentation: 

<https://github.com/jbuonagurio/proj.xll> 

I started this a couple years ago actually, but just recently changed it 
to use the native Excel C API and added some other improvements like the 
EPSG() function to return proj.4 strings from a giant switch statement 
(for single file deployment / separate folder and PROJ_LIB not 
required). 

I have a few improvements planned, but please let me know if you have 
any suggestions or feedback: 

- create an installer and chm help file
- test against GIGS
- use pj_is_latlong() so you don't have to use radians 

-----

On a somewhat unrelated note, I also started working on a library 
version of NGS HTDP, and a simple wrapper to use it in R: 

<https://github.com/jbuonagurio/RHTDP> 

The library isn't quite ready for prime time just yet - need to make a 
proper C binding with iso_c_binding (only works with GCC at the moment), 
add the required explicit interfaces and other cleanup. At this point 
the F77 code is mostly unmodified. 

I know you have the crs2crs2grid.py utility to generate HTDP grids 
between specific epochs, but I think it would be cool to embed HTDP in 
such a way that you can provide epoch dates as parameters in the proj.4 
string. Would probably take quite a bit of work to do this 'cleanly' 
though.

Thanks for the great software, 

John Buonagurio