Errors found when validating media-channel (from layer-0 YANG)

I mostly fixed all the errors of the module and now it is almost aligned with current version of layer0-types, layer0-types-ext and ietf-te-topology. Here is a summary:

Whenever a grouping of layer0-types was not found, we look for it in the current version. Most of them were just renamed so it was only a matter of finding the right one.
Some of the old groupings are no longer in the layer0-types. FEC was in layer0-types-ext but term-type, wavelength assignment and flexi-grid-path-bandwidth were eliminated without clear equivalents.
Some TE-topology paths were also wrong. In most cases, it was easy to update them but, in some cases, I didn't find an equivalent node in the current TE-topo doc. In these cases, I comment out those sections.
In layer-0-types, there is an error causing validation problems. In line 523, I think must '. >= min-slot-width-factor' should be must '. >= ../min-slot-width-factor'. If someone checks that I am right, we can report this to the authors.

Any help or comment is welcome with the last three points! :)

Originally posted by @dperdices in https://github.com/ietf-ccamp-wg/draft-ietf-ccamp-flexigrid-media-channel-yang/issues/1#issuecomment-772474262

ietf-ccamp-wg / draft-ietf-ccamp-wdm-tunnel-yang

Errors found when validating media-channel (from layer-0 YANG) #11