Packaging, installation, and licensing changes

For efficiency, Configuration options can now be written and read using a new set of constants: for example Feature.ALLOW_EXTERNAL_FUNCTIONS in place of FeatureKeys.ALLOW_EXTERNAL_FUNCTIONS. This avoids the expensive lookup using long string values. The old mechanism remains available but is deprecated.

If the configuration option Feature.ALLOW_EXTERNAL_FUNCTIONS is set to false, environment variables are no longer visible to the functions fn:available-environment-variables and fn:environment-variable (the behaviour is as if the environment variable did not exist). This brings these functions into line with the fn:system-property function.