bugfix: omelasticsearch does not work with broken/changed ES 1.0+ API

closes: https://github.com/rsyslog/rsyslog/issues/104

IMPORTANT: This is untested, as setting up the env is quite some pain
for me. I push this in order to get feedback from a couple of folks that
have committed to test out the patch. Do NOT consider this fixed until
it has been merged to the official "v8-stable" (or above) branch.
Merge branch 'v8-stable' into v8-stable-es-fix

Conflicts:
	ChangeLog
testbench: some plumbing for new es tests
Merge branch 'v8-stable' into v8-stable-es-fix
testbench: add test for elasticsearch errorfile (bulk mode)
testbench: test for errorfile in nonbulkmode added
omelasticsearch: properly handle errorfile in non-bulk mode

see also: https://github.com/rsyslog/rsyslog/issues/104
maintain ChangeLog and some nitfixes
testbench: add new ES tests to make check

also a quick nitfix