Add support of ElemHideEmulationFilter filters

[sergz]

Background

Issue #4394 introduces the new filter type, libadblockplus should also provide a means for third parties to use this functionality. However, to avoid any kind of confusion or having it unusable because of some missed parts, because the actual support of this feature should be implemented rather in a gluing part (which is integrating libadblockplus in a browser), there should be a real working example of how to use it. Therefore it should be done simultaneously (actually when we have resources) in one of libadblockplus clients, for instance libadblockplus-android's WebView.

What to do

Negotiate it with libadblockplus-android team after landing of #5475.

[sergz]

The following git commits can be helpful in order to adapt existing tests and to implement new tests or even get the essence of the functionality ​https://github.com/adblockplus/adblockpluscore/commit/92da9f3f6410955cbd271ccefef50f37b8e023e6, ​https://github.com/adblockplus/adblockpluscore/commit/29ecad10539abab28987979faa59417a6de27f00.