Updates to azgcorr (and azexhdf)

1. change to the arsf user
2. copy the release file to ~arsf/usr/arsf_releases/relXXX.tar.gz (rename to add .tar.gz)
3. uncompress to ~arsf/usr/arsf_releases/bill-YYYYMMMDD/ (where the date is the date of receiving, ish)
   1. mkdir ~arsf/usr/arsf_releases/bill-YYYYMMMDD/
   2. cd ~arsf/usr/arsf_releases/bill-YYYYMMMDD/
   3. tar xzvf ../relXXX.tar.gz
4. test it works! (need a regression test - see #12)
5. cd to ~arsf/usr/bin and symlink the new binaries there
6. ftp updated azgcorr and azexhdf to the ARSF ftp site (see ​http://rsg.pml.ac.uk/intranet/trac/wiki/Projects/ARSF-DAN/ARSF_FTP for login details, use mgrsw user), remove old versions as needed
7. Copy updated software to relevant section of the Downloads bit of the wiki here, attaching any restricted access items to Downloads/Restricted (normal staff login). Ensure all links are updated to point to the new software rather than the old.
8. notify neodc@… of the update, with a short description of what it is and a link to the FTP site
9. Add an entry on the ARSF google calendar on the date of azgcorr expiring, with an email reminder a few weeks beforehand. Use the command azgcorr -xdate to get the expiry date.