Read/Write mmcif/pdbx files

[gitoliver]

Perhaps this parser would make this easy to support reading writing these files:
readcif
Sounds like I can just include the header and source file and acknowledge:
"For simplest use, just copy the one C++ header file and source file into your code."
"The readcif library license is an open source license with an acknowledgement clause. So if you use it, acknowledge that fact in your documentation."

Here is an example where you extract the parsed info into an atom struct:
https://github.com/RBVI/readcif/blob/master/docs/readcif_example.cpp