Merge branch 'dev'
Release v1.1.0

Added: Support for taking snapshots of collections (see project wiki)
Added: 'Cascade' flag to attributes constructors (see project wiki)
Added: MementoCollectionAttribute
Added: Collection adapters
Improved: Moved exceptions and attributes to the 'MementoContainer' namespace
Removed: MementoClassAttribute cannot be used on interfaces anymore
Fixed: Property chain validation