Currently, you can't write version="@Strings.AppVersion" in your manifest.xml.
If you do, you get an exception like
BUILD: ERROR: com.garmin.connectiq.common.manifest.ManifestException: Problem validating the manifest file: cvc-pattern-valid: Value '@Strings.AppVersion' is not facet-valid with respect to pattern '[0-9]+\.[0-9]+\.[0-9]+(\.[0-9a-zA-Z_]+)?' for type 'versionInfo'.