Clarify ITS Module attributes definitions

In the section "5.9.12 Module Attributes" we define both ITSM and ITS
attributes, but mostly ITS attributes.

They usually have a definition that starts like this (using taClassRef as an
example):

[[
5.9.12.31 taClassRef

Text Analysis Class Reference - the taClassRef attribute exactly corresponds to
the [ITS] defined taClassRef attribute.
]]

The wording "...exactly corresponds to the [ITS] defined taClassRef attribute."
is, in my view, misleading as it does not state that
it is the ITS attribute itself. From the text and the lack of namespace
information, one could think the attribute is to be used
like this: <mrk id='1' taClassRef ='...'>.

It seems we should have a definition more like:

[[
Text Analysis Class Reference - the ITS taClassRef attribute
]]

With a link to the attribute in the ITS specification.

I know I have mentioned this for mtConfidence already
(https://issues.oasis-open.org/browse/XLIFF-36) but I think this is something
that should be addressed for all ITS attributes.