Update SectionFormat.md
Merge pull request #140 from OttoAllmendinger/pr-newarmor

Update SectionFormat.md
Message, xml tag and attribute renames.
Rename "asset contract" to "instrument definition contract" and issueAssetType to issueInstrumentDefinition.
Merge pull request #141 from benma/master

Message, xml tag and attribute renames.
Adjust heading levels, add menu metadata, misc. fixes.
Rewrap too long lines and fix layout.