Moved FormMail default texts to separate class (MailTemplates.cs), in order to be able to serialize/deserialize them to XML
Added configuration tab to edit Mail templates, still buggy (working on list of template fields / suggestions)
Added storage and loading of MailTemplates to xml database
Added form to enter BLZ/KTO instead of IBAN (with automatic IBAN calculation). This is a byproduct for Sparkasse-compatibility
Fixed Sparkasse CSV wasn't imported properly (Sparkasse now uses whitespace at the end of IBAN field, which led to failed comparisons)