Update CIViC docs with Assertion revision for NCCN

[arpaddanos]

Update Assertion docs with protocol for revising the NCCN guideline.

• guideline should be read before updating NCCN version
• update Assertion wherever needed to reflect the guideline
• add any new papers cited in the guideline relevant to the variant and annotation to Assertion in the form of new EIDs
• contact admin to enter the new guideline in the following format: disease v.xxxx
• make all the suggested changes

[susannasiebert]

contact admin to enter the new guideline in the following format: disease v.xxxx

If the guideline is new or the name has changed, contact admin to add this as a new guideline in the admin interface in the format: disease
The version is a separate freefrom text field and not part of the nccn guideline name itself

Also add documentation describing the format of the nccn guideline version field: x.xxxx (the leading v should be omitted)

[kkrysiak]

@arpaddanos can you provide a specific location in the docs and specific text you would like there?