Hidden Scald variables

There are some hidden variables that do not have an UI (yet?):

• scald_always_rebuild: Deactivate Scald caching
• scald_custom_contexts: contexts created by Scald UI. Export this variable if you want to export contexts (context configs are exported separated, as in general you don't export a context but only its config)
• mee_store_sas: Allow trusted editors to alter the markup
• mee_field_types: Textarea field types that allow MEE to be enabled (default: text_with_summary)