records: acl hook added to record documents.

* Add new model to represent documents attached to one or more records.

* Add pre hook to the default ACL to check user rights over the records
  that the document belong to.

* New record config variable `RECORD_DOCUMENT_VIEWRESTR_POLICY` to
  specify the access policy over documents attached to one or more
  records.

Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
linkbacks: jinja base templates renaming

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
messages: jinja base templates renaming

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
oauth2server: jinja base templates renaming

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
pages: jinja base templates renaming

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
records: jinja base templates renaming

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
cloudconnector: jinja base templates renaming

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
access: file renaming

*Moves files to `admin/` directory

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
search: jinja base templates renaming

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
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>