Resolve "FEATURE: Use time stamp from kurisu in update process"

Closes #109 (closed)

• New way of updating the db by re-using fileds when possible
• Check with the repo_timestamp in the repo module instead of getting the file's mtime
• Default the repo_timestamp to the file's mtime at upgrade time

src/database/disk.sql

@@ -15,7 +15,7 @@ PRAGMA foreign_keys        = true;
 -- Version mk-7.1:
 --      Add field 'misc.version'
 --      Add field 'kara.cached_mtime'
---      Add field 'kara.cached_dur'
+--      Add field 'kara.cached_duration'
 --      Make 'kara.author_name' field 'NOT NULL'
 --      Make 'misc.obfuscation' default to 1
 -- Version mk-7.2: