Additional logic to deal-to saving files:
- ENHANCEMENT: Added mime-type processor utility class
- ENHANCEMENT: Added sublcass of ExternalContent#Transform() to deal with _both_ files and pages
- ENHANCEMENT: Modified StaticSiteContentExtractor#curlRequest() to deal with largish files (hat-tip to @stojg)
- ENHANCEMENT: Modified methods that require mime-type awareness to ensure they are passed the relevant data