build: karma now reports with mocha formatter

build: karma now reports with mocha formatter

The progress reporter is quite nice to avoid spammy output to the
terminal, but it is not very human friendly when trying to find out what
is breaking.

Mocha has a very nice reporting organized as modules and list items for
each of the tests:

ext.cx.tools.template
  ✖ Equivalent template exists
  ✔ Adapting a template not existing in target language
  ✖ Adapting template having invalid title
  ✖ Template name and params adaptation using templatedata
  ✖ Template params adaptation using templateData - English to French
  ✖ Template params adaptation using templateData - English to Spanish

Add karma-mocha-reporter node module and make it the reporter.

Change-Id: Ic7d848b45e8e5ad3839d8a2bd822b63838319ad7