Implement new, rewritten logging for GuidedTour

Schemas linked from https://trello.com/c/Ldl4pvro/423-write-schemas-for-non-linear-guidedtour:
* Schema:GuidedTourGuiderImpression
* Schema:GuidedTourGuiderHidden
* Schema:GuidedTourButtonClick
* Schema:GuidedTourInternalLinkActivation
* Schema:GuidedTourExternalLinkActivation
* Schema:GuidedTourExited

Supporting changes include:
* Adjustments to how action buttons work
* Marking which buttons are semantically links, and which are external
* Putting logging in new EventLogger class

Change-Id: I5f6615767e88d5eb0c238aee9e17f36c9b7ac4c2
Remove guiders code that generates onclick based on button text

There was no i18n, this was not documented, and it did not fit the
rest of the architecture.

Change-Id: I87ff70394d8a23b9c2ee056afa2590687456e687
Merge "Remove guiders code that generates onclick based on button text"