Rotamer library

  Spock's rotamer library lives in the text file $SPOCK/lib/rotamer.lib. Currently this file is created by running the script dunbrack.sh on Roland Dunbrack's rotamer library from http://www.cmpharm.ucsf.edu/ dunbrack, which is also included in the spock distribution for reference. Users may substitute their own favorite rotamer library for spock's provided they follow the spock format: six space or tab delimited text columns. Column 1 is the three-letter amino acid code. Column 2 is the frequency of the rotamer, and the remaining 4 columns are for for the chi1-chi4 angles, with 0.0 for undefined angles. The data should be sorted such that the most common rotamer is listed first, and all rotamers for a given amino acid should be together.