BibUpload: indicators in strong tags

• So far CFG_BIBUPLOAD_STRONG_TAGS config variable assumed strong tags had empty indicator. This was causing tags such as 999C0 to never be matched. The new implementation assume strong tags specify also indicators. If they are not specified, then '%' is ussumed for ind1 and ind2. (closes #939)

Reported-by: Alessio Deiana <alessio.deiana@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>