InvenioConnector: mechanize dependency

* python-mechanize package is an optional Invenio dependency.
  However _SGMLParserFactory and CDSInvenioConnector classes
  in invenio_connector.py were assuming its existence.
  This is now fixed.

Reported-by: Genis Musulmanbekov <genis@jinr.ru>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
BibIndex: better wording for stemming in admin UI

* Improves the wording of the configuration form for the stemming
  setting, in order to better clarify how the system is affected
  by changing the stemming setting of an index.

Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
Merge branch 'maint-0.99' into maint-1.0

* maint-0.99:
  BibIndex: better wording for stemming in admin UI
Merge branch 'maint-1.0' into maint-1.1

* maint-1.0:
  BibIndex: better wording for stemming in admin UI
Merge branch 'maint-1.1'

* maint-1.1:
  BibIndex: better wording for stemming in admin UI
  InvenioConnector: mechanize dependency