Updated format for help and support

I updated the help and support draft in the new-format-for-help-module based on our conversation in the task force meeting on June 4, 2018 [1].  I basically followed Lisa’s proposed format and made the following changes:
1) I added all of the value types into the Vocabulary section. They were previously split up between alternative and helptype.  I added alternative, feedback, extrahelp, and helptype into this list.  If there wasn’t a definition I drafted one (although I wasn’t sure of a few).  Please review the definitions and file issues as necessary. 
2) I added a note that all of the current examples use attribute/value pairs but that does not imply it is the only implementation mechanism. 
3) Minor other editorial changes. 


[1] https://rawgit.com/w3c/personalization-semantics/new-format-for-help-module/help/index.html#addn-content <https://rawgit.com/w3c/personalization-semantics/new-format-for-help-module/help/index.html#addn-content>

Becky