updates can now perform simple expressions

[Jak Sprats]

checked into github yesterday.

it is not possible to perform SIMPLE expressions on columns during
updates.

Expressions like:
"count = count +1"
"num = num *4"
"events = events || ' new event'"
are supported.

I wrote this up (briefly) in the Command Reference
http://code.google.com/p/alchemydatabase/wiki/CommandReference?ts=1292497558&updated=CommandReference#Update_Expressions

UPDATE expressions currently support the following functionalities
(+=, -=, *=, /=, %=, ^=, ||=)

This is a small change, but is very helpful for simple constructs like
counters