Clarification for rrtype JSON format (feedback from dnsop)

String when known, Number when unknown
replace "zone file" with "master file" (dnsop feedback)

As RFC1035/RFC1034 mentions "master file" only.
rrtype: Resource Record (RR) TYPEs and not "DNS Label types" (dnsop feedback)
Reference to JSON added
rdata type clarification array

Multiple resource records -> JSON array
Single resource record -> JSON string
rdata clarification (dnsop feedback)

If resource records are multiple, an array is returned. Each record from the array
is represented as a JSON string.
If resource record returned is signle, it's a string.
zone file -> master file (dnsop feedback)
time_first and time_last are JSON numbers. (dnsop feedback)
Clarification for all JSON types. (dnsop feedback)
Clarification for JSON output
String value of resource records must be escaped as
defined in the JSON RFC.
Clarification of the sensor_id -> JSON string / note for escaping.

Aaron: could you check if your implementation is ok?
Typo fixed
Prepared for 02 publication
Prepare for 02 (to be published in February)
Update to the TODO (mainly to check with aaron)