add tests to DifferenceEngine and optimize each removal in it

fix: prevent two selected options, b/c apparently 'String' == 0 ��

There was a bug, where the options array ['Auto', 0, 1] would result in
HTML option tags where both the 'Auto' and the 0 option we

fix: prevent two selected options, b/c apparently 'String' == 0 ��

There was a bug, where the options array ['Auto', 0, 1] would result in
HTML option tags where both the 'Auto' and the 0 option were selected.

show more ...

fix file name
closes #2129

proper handling of "0" as a search query in media manager + test case for this

create some unit tests that test searching in media manager

test: add tests for the section edit regex

reworked notifications to the test system

No globals required anymore, somewhat more general approach to sending
data to the test system. Clean access through keys.

move test page somewhere else to not interfere with other tests

another go at working around the networink troubles at travis #2109

adjusted the tests

Test code for workflow 'show - sectionedit - save/cancel' (with modifications in test classes and 'send_redirect()' and 'act_dispatch()'.

show more info on failed HTTP requests

hopefully this will help with figuring out why our HTTP tests sometimes
fail on travis.

some cleanup fpr set_metadata test

added one more test for internal links

just to be sure, we're not breaking something simple here.

parsertests: replaced var keywords and added type hints

Add tests for array_replace part of set_metadata

response on review

response on review

cleaning

extracted functions
added test coverage

cleaning after better understanding of the surroundings

back slashes in @import

cleaning

fix tests on windows

added tests for legacy function tpl_get_action()

I want to make this function use the new Menu Items, these tests should
ensure I don't break functionality.