Remove the htmlok and phpok embedding options

Both options have grave security implications and novice users seem to
ignore advice about them. In the last decades I never came across a wiki
that had

Remove the htmlok and phpok embedding options

Both options have grave security implications and novice users seem to
ignore advice about them. In the last decades I never came across a wiki
that had legitimate use of these options.

If someone needs the functionality, it can easily be added back using a
plugin. But I prefer to give users one less option to shoot themselves
in the foot.

Removal of the translations for the config strings can follow after this
has been merged.

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move test page somewhere else to not interfere with other tests

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