Fixes #22 plus a few other issues found in MetaData parsing

• The Comp visitor did not strip double quotes from StringLiteral mimetype and name values, but the Instr/Instance visitor did. Now all variants strip the surrounding quotes (if a name has spaces, the quotes get added back for C output purposes).
• The Instance visitor incorrectly identified the source of any MetaData as coming from a component definition file
• The Instance visitor also incorrectly identified the source name of any MetaData as the name of the metadata.