PP for interval join with BAMDataSource

[mwiewior]

Write unit test and document if in this query for BAMDataSource interval pushdown works if BAI is in place.

SELECT s2.targetId,count(*)
    FROM reads s1 JOIN targets s2
    ON s1.chr=s2.chr
    AND s1.end>=s2.start
    AND s1.start<=s2.end
	AND s1.chr='chr1' AND s1.start > 10000
    GROUP BY targetId;