widgets autogen v2

[KaruroChori]

There are several changes needed to the widget auto-generation or code:

• New schema to support missing features, like the semantic flag and splitting fields into getter, setter and parser methods.
• Adapt the older codegen code to use the new schema
• Adapt all schema files to the new format
• Complete the getter/setter interface at for embedded C scripts
• Complete the getter/setter interface at for embedded JS scripts
• Move parser and serializer helpers in a better place
• Expose the special value field for widgets like fl:input, so that we can use them later on for stored secrets.
• Remove the previous code & check for ood documentation based on that.
• Base the parser on the code generated via xml.piler

[KaruroChori]

I evaluated some of the alternatives, and I deemed frozen not to be suitable because of lazy-eggplant/vs.templ#7
Dispatchers will be most likely implemented via gperf.