Add cache of match failures

This change introduces an sqlite database that contains the track_id,
db insertion time, and ttl in the cache. The ttl starts with one week,
and increases exponentially by a factor of 2 each time the same track_id
is added to the database.

This significantly reduces the execution of the time script when there
are a lot of match failures accumulating, which do not need to check
every time.

.gitignore

@@ -1,7 +1,7 @@
 # Config and cache files
 config.yml
 config.yaml
-.cache-*
+.cache*
 .session.yml
 
 # Byte-compiled / optimized / DLL files