RFC 8040 Sec 3.1
* non-pretty print remove all spaces, eg `{"operations":{"clixon-example:client-rpc":[null]`
* Replaced JSON `null` with `[null]` as proper empty JSON leaf/leaf-list encoding.
* [Cannot write to config using restconf example #91](https://github.com/clicon/clixon/issues/91)
* Updated restconf documentation (the example was wrong)
* [clixon-lib yang revision file name update #92](https://github.com/clicon/clixon/issues/92)
* Clixon-lib yang file had conflicting filename and internal yang revision.
* This was only detected in the use-case when a whole dir was loaded.
* Inserted sanity check in all yang parse routines.
* Committed updated clixon-lib yang file that triggered the error
6df434093e
