sorting support for syntax plugins, info plugin now actually does something

Syntax plugins now need to implement getSort() which should return a number.
This number is used to add all syntax modes in the correct order. To see a
list in which order current modes are loaded you can use the info plugin like
this:

~~INFO:syntaxmodes~~ lists all known modes (includes existing plugins) with
their sorting score

~~INFO:syntaxtypes~~ lists all syntax types and their registered modes (useful
for implementing the getType() function.

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