BibIndex: virtual global index

• Turns global index into a virtual index and hanges indexing engine to index virtual indexes during indexing physical indexes. (closes #1574)

• Creates new idxINDEX_idxINDEX table which stores information about virtual indexes and their dependencies.

• Modifies functions for searching for affected indexes to be aware of virtual indexes.

• Adds miscellaneous index and field.

• Adds new tags for miscellaneous index.

• Enhances bibindex administration interface accordingly.

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>