Implement File -> Create or Update Tag

[cyclops1982]

Set a single tag on a file.

Make sure the description of this method is "Create or Update a single file tag"

Input values:

• FileId (text)
• Tag Name (text)
• Tag Value (text)

Output:

• Same as GetInfoById

Input validation:

• If folder doesn't exist:"File'{FileId}' does not exist"
• If the tag does not exist, then ADD the tag to the tags