Add rudimentary spell check for specification

We can't easily spell check the entire specification, the
pseudocode and operator tables make it unworkable. This
adds a simple python script that tries to extract just the
description of the operators for checking. It also does a check
over the entire license.

A custom dictionary is used to contain specification custom words.

Change-Id: I74558c03af1506e2970f20b3246d920c2753ca44
Signed-off-by: Eric Kunze <eric.kunze@arm.com>