browsertests: profile for default settings

Some scenarii are meant to be tested on specific wiki instances such as
commmons.beta.wmflabs.org or sandbox.translatewiki.net. For the Gerrit
integration, we are using a fresh wiki having the default ULS settings,
hence the specific tests will definitely fail.

This patch introduces a new cucumber tag `@needs-custom-setup`, it is
meant to flag tests which require further configuration tweaking, for
example tests explicitly targetting an already existing wiki such as
beta or translatewiki

I am introducing a new cucumber profile 'ciwmf' which exclude any test
tagged '@needs-custom-setup' or '@phantomjs-bug'.  That profile is going
to be used by the Jenkins/Gerrit install using something like:

  cucumber -p ciwmf

equivalent to:

  cucumber -t '~@phantomjs-bug' -t '~@needs-custom-setup'

Marked some tests as being bugged on phantomjs:
* autonym ones because of bug 57101 "browser tests must normalize
  font-family".
* accept_language since we dont have yet a way to pass the accept
  language header via phantomjs.
* Commented out an 'input method is visible' test with Vector + Hebrew
  since it does not pass.
* Malayalam link is looked by title which is translated by default.

This patch is passing on my local wiki, albeit skipping a lot of steps.

Change-Id: Ib055f5470886e1b818d4c53cb4c61a751d81e154