Shortcodes refactor

[deanmarcussen]

Related to #6199

• Implements Shortcodes parser by @sebastienros
• Renames ShortCode to Shortcodes as I got it wrong :(
  The rename includes files, folders, and csproj, so will create a new nuget package name. We did this a while ago with the Github to GitHub change, and it worked ok, so I think is ok to do it.
• Renames interfaces, and removes unecesary interfaces
• Implements the [image] shortcode using the new parser

Has one issue with the MarkDig processor which replaces " which and html encoded version, so arguments have to be used with a single quote, not a double quote.
Need to look further into that issue.

Does not include

• The shape Shortcode I demoed a week ago, still deciding if that's useful
• Admin editable Shortcodes. That's for another pr

Wanted to get some progress going however, with the changes that are necesary, and was wanting to implement a Shortcode yesterday, but didn't want to because it will be so trivial with the new parser