Fixes cofoundry-cms#507 - Internal Server Error when attempting Delete

Removed password field boundary validators to prevent misleading erro…

…r messages coming up e.g. "password must be more than 6 characters" when the configured lower boundary is greater.

Made it easier to override or extend the AuthenticationBuilder

Fixes cofoundry-cms#458 - Comments in Page Template files break regio…

…n detection

Fixes cofoundry-cms#401 Cofoundry.Web.Admin.Internal.VisualEditorActi…

…onResult.ExecuteResultAsync fails with "Synchronous operations are disallowed"

Fix to FE build script to allow different base urls, supporting plugi…

…n builds.

Clarified contact and contribution guidelines.

Merge branch 'master' into feaure/360-netcore-3-1

Fixes cofoundry-cms#309 - Links in admin email templates do not accou…

…nt for a custom admin directory. Note that this is a temporary fix as this area is being reworked in the Cofoundry v0.7.

Merge branch 'release/v0.6.0'