Create sendToTrackers helper
Create sendToTrackers helper

Simplify tracker object by moving for loops into a single method which
gets passed the function to call on each tracker and the arguments to
give it.

Add some protection against methods not existing on the trackers.

TFOH/govuk_frontend_toolkit,TFOH/govuk_frontend_toolkit,alphagov/govuk_frontend_toolkit,TFOH/govuk_frontend_toolkit,alphagov/govuk_frontend_toolkit,quis/govuk_frontend_toolkit,alphagov/govuk_frontend_toolkit,quis/govuk_frontend_toolkit,quis/govuk_frontend_toolkit,TFOH/govuk_frontend_toolkit,alphagov/govuk_frontend_toolkit,quis/govuk_frontend_toolkit