started work on bptree port

Signed-off-by: Tim Henderson <tim.tadh@gmail.com>
lots of work on writing the insert logic, go leaf insert and split done

Signed-off-by: Tim Henderson <tim.tadh@gmail.com>
put seems to work

Signed-off-by: Tim Henderson <tim.tadh@gmail.com>
b+tree implementation - removal

Signed-off-by: Tim Henderson <tim.tadh@gmail.com>
support for remove and b+map

Signed-off-by: Tim Henderson <tim.tadh@gmail.com>
Merge branch 'bptree-port'