First version of sequence matching.

The most important function GAS-SEQ:FIND-MATCHES was added.  It
returns an alist, in which CARs are lengths and CDRs are lists of
matching points in the input sequences, every point being a CONS with
locations in the input sequences.
[Git] Ignoring Emacs backup files.
Moved the GAS-WORK package definition higher so that it can be
referenced by the GAS-COMMANDLINE package.
Some Fasta files have no header line so we use the filename as the
sequence identifier.
I forgot to update variable names after the last change in the Fasta parser.
Command-definition code was reorganized.
Now we store a doc-string for every defined command.
ABIF format support was added:
- in package GAS-ABIF, there is a function PARSE-ABIF-FILE that
  returns the most important information from the given ABIF file;
- in package GAS-WORKSPACE, some code was added to handle various file
  formats, most notably GAS-WORK:HANDLE-FILE (while the function
  GAS-WORK:LOAD-SEQUENCE was changed to call this new function instead
  of doing everything on it's own).
Fasta: corrected the case of multiline input.