1.0.0-beta.3

• Breaking change: Updated Statiq Framework to version 1.0.0-beta.20.
  This version of Statiq Framework contains breaking changes which Statiq Web will inherit.
• The Content pipeline no longer creates any metadata-based tree structure (I.e. the metadata key Children is no longer set). Instead, consider
  using methods from Outputs such as Outputs.GetChildren(doc) or the new OutputPages property (see the Statiq Framework 1.0.0-beta.20 release notes for more details).
• Added a new MinimumStatiqWebVersion key to perform a check for the minimum allowed version of Statiq Web. If this is set to something higher than the current version
  of Statiq Web, an error will be logged and execution will stop. Any setting that starts will this key will be considered, so it's recommended the use of this key be
  suffixed with a unique identifier to avoid conflicts between components (for example MinimumStatiqWebVersion-MySite). While not required or typically necessary for sites,
  it's recommended that themes set this in their theme settings file (for example MinimumStatiqWebVersion-CleanBlog).