My edits to the current SAWSDL Spec

All,

I would like to propose the following edits to the current SAWSDL spec
in preparation for publishing the second draft.

These edits mainly address the point many of us (including Claudio,
Laura, and myself) have brought up about adding enough explanation in
the spec to help a reader understand why one needs to use extensions
such as modelReference and liftingSchemaMapping and
loweringSchemaMapping. I have added significant background context and
information throughout the document to make it more reader friendly.

If my contributions/edits are accepted, it probably would make sense
for me to be an additional editor of the SAWSDL spec - per Jacek's
offer in the first face-2-face meeting. If that is the case, I would
be glad to make these changes directly to the spec.

Regards
Rama Akkiraju