More CCR code cleanup

Random constants are bad. Let's use the indices that we already calculated
(and true and false if we mean boolean values).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
User manual: text to explain filter panel

Few smaller changes to text dealing with tissue pressures graph

Signed-off-by: willem ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Small modification of the filter description

This seems more important to explain - it's OR within the column and AND
between the columns.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>