Print warning if preview version

[liliankasem]

Issue describing the changes in this PR

resolves #issue_for_this_pr

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• I have added all required tests (Unit tests, E2E tests)

Details

• Refactored the CliVersion prop so we get the full version and not the assembley version. This ensures that when func --version is called, the user should see 4.0.8050-preview1and not just4.0.8050`.
• Updated project version to add -preview1 suffix
• Implemented WarnIfPreviewVersion method to notify users that they are on a preview version of the CLI. This should print when in preview when func, func --version, func init, func new, or func start is invoked.

[mattchenderson]

I do wonder about the warning being before the actual printing of the version in effect, but I see the comment thread there. I think it is more consistent if always the first thing, which overrides my personal preference for it coming after the version is actually printed.

Small wording change requested just to make things a bit clearer for some of these actions.