MARMOTTA-155: Add test for invalid language and use Locale.Builder

Locale.Builder throws an exception instead of returning a partial representation for illformed BCP47 language tags
add an additional test to verity that the error described in MARMOTTA-283 does not happen anymore (or at least cannot reproduced)
configuration service mapped list to strings, which was a bug. commit fixes MARMOTTA-231
set correct links (partly fixes MARMOTTA-149)
set content from marmotta webpage to security about page (partly fixes MARMOTTA-149)
fixed MARMOTTA-280
merge
change status code of SPARQL timeout to 504 to prevent Firefox from retrying the request immediately (MARMOTTA-280); patched SNORQL so it displays a nicer error message in case the SPARQL query fails
MARMOTTA-155 : Switch to an ill-formed language tag

The language tag "invalid" is not ill-formed according to BCP47, although it is not registered.

The underlying issue that caused the test to fail was due to the SQL database scheme restriction VARCHAR(5) on the language tag field.