Gbib auto updates

By default the Gbib checks every 5 seconds if a flag file on the hgDownload server is more recent than the date of the last update of the Gbib.

If the file on hgDownload is newer, it will start the update:

1. Update the update script itself from hgwdev.soe.ucsc.edu/browserbox and also update the hg.conf from there
2. Update all existing /gbdb files
3. Update all mysql files + patch the hg19 searchspec and hide some tracks on hg19
4. Update all hgcentral files + patch the blat server table

Will have to move updateBrowser.sh and hg.conf to hgdownload for release.