Add support for reading metadata from anabat files

[atruskie]

Anabat file format documentation for zero crossing files (.zc): http://users.lmi.net/corben/fileform.htm#Anabat%20File%20Formats

Reference implementations:

• https://github.com/riggsd/zcant/blob/master/zcant/anabat.py
• https://github.com/WavX/bioacoustics/blob/master/R/read_zc.R
• http://[users.lmi.net/corben/loader.txt](http://users.lmi.net/corben/loader.txt)