Feature/add limit to test histories

[AlexNetcare]

This PR would add a couple things to the Test Histories.

1. An additional Property on a page to disable Test Histories for that page. This is turned off by default.
2. The behaviour when purging Test Histories would now change to only delete Test Histories of the current page. Additionally, an extra Button, next to the purge Buttons, to still purge globally can be checked.
3. Two new Properties for the plugins.properties:
   • TestHistory.maxCount=10 would define that only 10 Test Histories per page should be saved. This is off by default.
   • TestHistory.purgeTime=0,30,60,90 defines the purge Buttons on the Test History page. Currently will default to 0,30,60,90 when nothing else is configured.

Depending on the configured purge times, the GUI for the Test Histories would look like this:

By coincidence this might be taking care of this Request #1488
The new Property does not work recursive though.

[AlexNetcare]

These might be more changes than it should be for a single PR. I will make smaller PRs for each point individually.