assets: less flavor of bootstrap

* Installing less and grunt-contrib-less.

* Adding the filters parameter on the assets.
  `{% css "foo.css", "00-bundle", "less" %}`

* Adding some configuration keys.
  LESS_BIN which must be pointing to lessc.
  CLEANCSS_BIN ditto for CleanCSS
  LESS_RUN_IN_DEBUG (default True) to enable or disable the less
  bundling in DEBUG. ASSETS_DEBUG must be also set to True for
  it to work.

* Renamed base.css to base.less and it includes the less files from
  Bootstrap and Font-Awesome.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
docs: fix of sphinx warnings.

* Fixing all the warnings given by sphinx during compilation.

* Fixing the PEP8, PyFlakes and PEP257 warnings of the touched files.

* Adding some intersphinx.

* Reading the theme from docs/requirements.txt.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
merger: syntax fix

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
assets: fix bundle builder

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
assets: error logging if binary are missing

* Adding a check for LESS_BIN and CLEANCSS_BIN presence at startup.
  It switches to ASSETS_DEBUG=True if you ignore the error message.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
Reported-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
upgrader: fix for docstring style

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
elasticsearch: initial commit

Signed-off-by: Johnny Mariéthoz <Johnny.Mariethoz@rero.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>