unit tracking, requestcontext, documentation

Removed deprecated RequestContext calls and implemented custom
workaround to access/set message properties using the request path. New
component class ResponseHeadersToMessageProperties will pull the headers
off of a response object and set them as Session scoped properties on
the mule message before clearing all outbound scoped properties. In REST
APIs, new method is used to create a ResponseBuilder object for this new
component to use. The Method will set the path parameters as Response
headers with a generic OK response, which is thrown away by the end of
the flow with the HTTP Response Builder components. Incident numbers
were added to mroe paths to remove the need for the TenantInfo class
which was accessing path param information directly from the XML data,
which was unnecessary.

Created new database tabled "responding_units" which will be used to
track/reference the unit numbers which have been assigned to or have
claimed any given call. A new component was added, which is called
asynchronously, to write the unit number to the database after updating
the "assigned" flag in the caddata table. This unit number table is for
backend access only and should not be needed for sending data to
clients. Updated flows to utilize this new component and set the unit
number as a Session scoped message property (possible not needed; might
be accessible through inbound properties scope). Updated REST API which
creates a new PCR for a client to check the client's unit number to see
if the given unit is assigned to the call and, thus, has permission to
receive an ePCR for this call. REST documentation updated again to
reflect this change.