PATCH: Add missing nodes to graphical explain plan

Hello,

Per recent discussion on pgadmin-support ("index only scans are not
shown graphically"),

JFO> Insert
JFO> Update
JFO> Delete
JFO> Foreign Scan
JFO> Index Only Scan
JFO> BitmapAnd
JFO> BitmapOr
JFO> Values Scan (shows up as a Seq Scan)
JFO> LockRows
+ Merge Append.

Please note, that besides 10 new icons there are two icons for
existing nodes in the attachment, Bitmap Heap Scan and Bitmap Index
Scan.
I've changed them for unity with BitmapOr, BitmapAnd, which hopefully
will result in an intuitive understanding of the concept by users.
But I was thinking of bitmap index scans as an analogue for Oracle's
bitmap indexes. Then I've read explanations by Tom Lane
http://www.postgresql.org/message-id/12553.1135634231@sss.pgh.pa.us
and it appears that Postgres doesn't build literally a chain of 0's
and 1's, but an array of tuple pointers. Nevertheless, if it is
possible, I'd like these two icons to be committed too. You decide :)

--
Best regards,
J.F.