more documentation around Device Profiles

[jpwhitemn]

More documentation is needed around the device profile (per Core WG meeting 3/29). Specifically, what is the structure, what are the allowed elements, what is optional. There is a block diagram of the design of the profile (and profile document) on the Wiki today (https://docs.edgexfoundry.org/Ch-DeviceProfile.html) but much more is needed.

[mhall119]

Update the current Ch-DeviceProfile.rst with content from https://docs.google.com/document/d/1aMIQ0kb46VE5eeCpDlaTg8PP29-DBSBTlgeWrv6LuYk/edit#heading=h.qxpm8b64bzqz

[tonyespy]

@jpwhitemn is this still valid? I think the only thing that I see missing re: device profiles in the V2 documents is a decent description of how the device profile auto-import function works (same for devices too). There are bits and pieces scattered here and there, but the basic functionality (i.e. on startup, the services looks for YAML device profiles in Device.ProfilesDir and will import any new profiles found.