Allow submodules to be written in ragg language

[dyoo]

mye asks: Is there a reason the BNF based syntax doesn't work for submodules? (I'm assuming this is possible with the submodules which it might not)

The major obstacle I see to this is use of "#" for line comments, which might not work nicely with the Racket reader.

[dyoo]

See the sexp branch for a possible solution to this. It includes the ragg/sexp/lang language, which submodules can use.

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The other obstacle is that of alternation, which uses the pipe symbol. This conflicts with escaped symbol notation. The workaround I've got is to use "||", and check for the empty identifier. The hack is messy; I'm not positive yet that this is the right solution, but it appears to work so far...