move tests to unit test
enable delimited payload token filter

closes #3859
fix bug in term vector api, payloads were not handled correctly when some where missing

The array holding the payloads (TermVectorFields.payloads) is reused for each token. If the
previous token had payloads but the current token had not, then the payloads of the previous
token were returned, because the payloads of the previous token were never invalidated.
For example, for a field only contained two tokens each occurring once, the first having a
payload and the second not, then for the second token, the payload of the first was returned.

closes #3873
[DOCS] Add doc for delimited payload token filter