AbstractJUnit4BaseTest: Copy getRandomLatinString() from deprecated
DatabaseBasedTest

- Deprecates the one in DatabaseBasedTest, so copypasting it is fine
as the other one will then be removed someday.
 - Will be needed for fixing SubscriptionManagerFCPTest to compile
against AbstractJUnit4BaseTest being the new base class
AbstractJUnit4BaseTest: Copy addRandomOwnIdentities() from deprecated
DatabaseBasedTest

- Improved JavaDoc is added.
- getRandomInsertURI() is used as it was recently added to replace
getRandomSSKPair().
- Deprecates the one in DatabaseBasedTest, so copypasting it is fine
as the other one will then be removed someday.
- Will be needed for fixing SubscriptionManagerFCPTest to compile
against AbstractJUnit4BaseTest being the new base class
AbstractJUnit4BaseTest: Copy getRandomTrustValue() from deprecated
DatabaseBasedTest

- Deprecates the one in DatabaseBasedTest, so copypasting it is fine
as the other one will then be removed someday.
- Will be needed for fixing SubscriptionManagerFCPTest to compile
against AbstractJUnit4BaseTest being the new base class