refactor: optimisation around stoptimes

- moved stoptime related functionality into new core:data:stoptime module
  - will feature all the different realtime stoptime sources to be
      integrated later
- create proper database schema for future migrations
- deduplicate trips into stoppingpatterns, since many trips share the
  exact same stopping pattern
  - stoptimes are now linked to stoppingpatterns instead
  - stoppingpattern ids are generated from a hash composed of all stoptimes
- stoptimes now use deltas for arrival time to save space

server/src/main/resources/logback.xml

@@ -14,7 +14,7 @@
             <pattern>%d{YYYY-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
         </encoder>
     </appender>
-    <root level="trace">
+    <root level="debug">
         <appender-ref ref="FILE"/>
         <appender-ref ref="STDOUT"/>
     </root>