Fix invalid/suspicious extension keys in extensions.xml.gz

Assuming, a valid extension key must not contain upper-case letters, file extensions.xml.gz contains some invalid/suspicious entries. I assume the issues exist in the underlying data storage rather than in the creation logic that generates the XML file.

• invalid extension key: flvStreamPlayer
• invalid extension key: meta_CAS
• invalid extension key: AjaxChat
• invalid extension key: tom_FMENU
• invalid extension key: dmc_highPerformance
• invalid extension key: Oblady_questionnaire
• invalid extension key: SBuniplug
• invalid extension key: SBumfrage
• invalid extension key: SBbanner
• invalid extension key: theFormEval
• invalid extension key: theFormConcept
• invalid extension key: lilURL
• invalid extension key: RealURL
• invalid extension key: Vertretungsplan