Provide ability to debug element hiding filters

Background / User story

In eyeo/adblockplus/adblockpluschrome#172 (closed), we added the ability to and a preference to enable highlighting of elements that are affected by element hiding filters. Therefore what's left for us to do is to expose this to filter authors via the UI and to make adjustments to the styles used to highlight those elements.

See trac#4476.

What to change

• Design: https://eyeogmbh.invisionapp.com/public/share/KV16R40SHJ & https://eyeogmbh.invisionapp.com/console/share/SR17QG1V38/478451467
• Research: TBD
• Legal: https://jira.eyeo.com/browse/ABPUI-34
• Spec: eyeo/specs/spec!338

Hints for testers

None.

Hints for translators

Added the following strings:

• options_customize_elemhideDebug
• options_customize_elemhideDebug_tooltip

Integration notes

None.