binds the xapian-indexer with the dataset - should only be one dataset at a time
sub {} to init the xapian db on disk, prior to an indexing or searching operation
pass on the search id to allow the Xapian search plugin to distinguish between simple and other searches
re-use EPrints::Xapian db connector (probably EPrints::Xapian should be part of its ISA
)
partial support for advanced searches (re-use EPrints' default search definitions in the local conf to know which metafields/indexes to use)
partial support for satisfy_all flag
partial support for EPrints ordering methods in search definition (still default to Relevance ordering)
TODO: cleaner way to get the search conditions -> some metafield/index types (MetaField::Text / text) require a Xapian Query Parser (for stemming etc) while others (::Set, ::Id...) require a normal Xapian Query (via OP_FILTER, the efficient way to switch on absolute values (example: type:article, eprint_status:archive, subjects:AM etc))
inits/caches stemmer and stopper for every configured language in the repo (still need to plug this to the actual indexing of language dependant metafield type like Multilang)
makes it possible to re-use the default EPrints search definition (for simple searches) and includes the defined fields (as 'q') to the Xapian unprefixed search data
considers that any fields can be indexed (unless the core property 'text_index' is set to '0') and allows to over-ride such field definition to declare a specific indexing method (eg. the 'documents' field uses the 'index_fulltext' xapian indexing method)

all in all, this makes it possible to re-use the old format of search definition (->{search}->{simple} and others)

TODO: detect which ordering methods are defined in the old format of search def and automatically include these in the indexing scheme
defines some default ordering/indexed fields for eprints core fields - eprint_status and metadata_visibility must be declared because eprints searches automatically add dataset filters when searching (not to have items leak out of 'inbox', say)

note for Jaidi: watch out, this disables the bootstrap-based PaginateXapian module by default