FIX: reference for SHA-1 and typo
change default catalog TTL to 15 minutes
update catalog counters enumeration
add Repository Manifest section and revise signature description
FIX: typo
Merge pull request #10 from reneme/repo_manifest

Description of Repository Manifest and Signing Procedure

This adds a section about the Repository Manifest (.cvmfspublished) describing its purpose and the contained meta data fields. Additionally this revises the section about repository signatures and explains it in a bit broader detail. Finally it adds the new catalog statistics fields and changes the default catalog TTL to 15 minutes.

Also includes minor typo and reference fixes.