Added the property 'propagateFailure' to the mojit instance object and added a section in the composite mojit chapter about how to propagate child mojit errors to parent mojits.
Updated table for the specs object to include a table for the mojit instance object (user-defined).
Made copy edits.
Updated section on child mojits propagating errors to children with more details and with more precision.
Made a copy edit.
Merge pull request #1003 from zhouyaoji/docs_propagateFailure_property

[doc] Added documentation for the new  `propagateFailure` property that allows child mojits to propagate errors to parents.