Ietf 118 mod ver updates (#217)

* Fix #207

* Remove contentious whitespace text #208

* Fix T5, ambiguous imports #209

* Removes revision-label & scheme, fixes #210

* Reformat source file + regenerate

* Soem changes to support #211

* Proposed text for #221

* Renamed ietf-yang-library-revisions to ietf-yang-status-conformance
#215

* Fixed YANG validation issue caused by extra " in description of recommended-min-date
#225

While in there, also replaced remaining instances of recommended-min by recommended-min-date.
Removed rev:label from the 2 YANG modules since the label extension is gone.

* Removed remaining instances of revision-label-scheme.
#224

* For "recommended-min-date", do a date comparison. Modified other related text.

#213

* Making yang-semver an informative reference in module-versioning

#212

* recommended-min-date can not be used multiple times per import statement.

#228

* Reorder labels as per #211

* Minor tweaks during Feb 20 call

* Removed text which mentions labels (except for the example in 3.4)
#227

Some fixes wrt "recommended-min-date"
#213

Small cleanups too.

* Fixed incorrect yl-rev prefix.

* Further minor changes and cleanup

* Change elided to ommitted, update .txt file

* Addressed comments from Rob and Jason.

* Incorrectly put " in YANG description, replaced with '

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Co-authored-by: Reshad Rahman <[email protected]>