HTML-syntax change part 4 (missing parts)

[jakub-g]

Opening this issue for reference - some missing parts that were not handled in #323:

• args and ctrl can have only "value" inside double quotes, not inside single quotes unlike other attribs
• HTML syntax part 3 #323 introduced export-module which when parsed sets node.isExportModule = true for now in the syntax tree but nothing more than that (it doesn't perform the exporting functionality)
• no checking for multiple conflicting exports, export-module etc
• export can have value <template id=foo export=bar> and then block.modifier.exportName is available (null if not set), but nothing is done with it further, it's just parsed (template is still exported as foo instead of bar)