more fields and logs from trackable page

[nagisml]

Additional fields for TBs like origin, releaseDate
Provide the already loaded lastTBLogs from the first loaded page (up to ten logs).

[FriedrichFroebel]

Thanks for the PR.

Doing some quick skimming through the code, there are some things which probably should be addressed:

• As documented in the contribution guide, please add tests (and docs if relevant) as well.
• Why are you re-parsing the source tree for retrieving the logs?
• We might want to move the log parsing functionality to a dedicated method to keep the parser methods more readable (see the corresponding methods for Cache objects for an example).