Improve/fix block params in HTML syntax for components

(a) Added validation for the parameter identifiers, using a regex of the invalid characters based on the regex Handlebars uses for validating IDs
(b) Fixed cringeworthy bug in my previous PR due to `replace()` being called with a non-global regex
Can you pull this out into `var ID_PATTERN` or something? You can do `ID_PATTERN.test(param)` to be a bit more succinct.