written XML formatting for new zebra-specific elem set 'zebra::' which lets you dump...

written XML formatting for new zebra-specific elem set 'zebra::' which lets you dump the exact content of indexed fields in records.
Using for example elemset 'zebra::dc_title' dumps only the physical string index 'dc_title' fields in the virtual, from indexes constructed, record. Usisn 'zebra::dc_title:w' dumps only te subset of those which are indexed as type 'w'.

Added test record for oai-alvis example with utf-8 sequences and nasty XML escapes. Testing works on GRS-1 filters, but yet not on 'Alvis' filters, the direct YAZ function    zebra_storekeys_fetch in index/retrieve.c seems not be called at all .. more debugging needed.