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

inc/lektor/database.h

@@ -67,6 +67,7 @@ bool database_queue_get_current_file (lkt_db *db, char filepath[PATH_MAX]);
 
 bool database_get_kara_id           (lkt_db *db, char filepath[PATH_MAX], int *id);
 bool database_get_kara_path         (lkt_db *db, int id, char filepath[PATH_MAX]);
+bool database_get_kara_path_no_cache(lkt_db *db, int id, char filepath[PATH_MAX]);
 bool database_get_kara_position     (lkt_db *db, int id, int *pos);
 bool database_get_kara_mtime_id     (lkt_db *db, int id, uint64_t *mtime);
 bool database_get_kara_duration_id  (lkt_db *db, int id, uint64_t *duration);