Remove row crc computation

Remove row crc computation

This computation did not make sense anymore since we began to put the
contents in the Row object. The fact that it worked was a coincidence.

Instead, we set rows as changed() on creation and reset that once they
have been drawn. This will allow in the future for a finer definition
of what to redraw or not.

Also update the PAINTING_ANALYSIS document

(cherry picked from commit 9e2da4a3eac83f46ab184ea8d674f84643814017)