Populate FILTER_CONDITION of DatabaseMetaData.getIndexInfo for Firebird 5.0 partial indexes

[mrotteveel]

Firebird 5.0 introduced support for partial indexes. Support for this needs to be added to DatabaseMetaData.getIndexInfo by populating the FILTER_CONDITION column. Its value should be the <search_condition> of the WHERE <search_condition> clause.

Note that Firebird includes the where part in the RDB$CONDITION_SOURCE column.

Consider backporting to Jaybird 5.

[mrotteveel]

Stripping out the WHERE from the condition source has complications, as it will also store any comments before it, so for now I'll leave it in, with a remark in the javadoc that this may change in the future.