Added a classifier for module-opening sentences
Added support for Module tags to CoqVernacFileImpl

Modules, like sections, are closed with a sentence of the form "End foo.",
so this commit also makes a few extra changes to support that
Consider "Abort." to be a valid proof-ending sentence
Added support for Fixpoint and Inductive tags to CoqVernacFileImpl
Added support for jumping to Module, Fixpoint and Inductive sentences

This code is getting quite repetitive! Adding a new class to represent
named CoqScriptGroupDispositions would probably be a good idea
Improved OpenDeclarationHandler's support for Coq identifiers

This doesn't support Unicode characters yet, but neither do the sentence
classifiers
Added support for single-quotes in identifiers to the sentence classifiers
The Coq builder should use model sentences when calculating dependencies

Now that the model is beginning to be widely used, there should probably be
some kind of cache eviction policy to keep memory usage down
Removed the parameter from the ParserStack.popContext method

Clients were essentially obliged to call this method with the return value
of the getInnermostContext method. This commit simplifies things enormously
by always returning the innermost context
Added support for a version of the visitor pattern to the Coq model
Added an extractor object for matching named Coq script group dispositions
Use the model's new visitor pattern support in OpenDeclarationHandler

This should make it very easy to increase the scope of the search
Made OpenDeclarationHandler search entire projects for identifiers

This search strategy is far too aggressive -- dependencies and scopes are
both ignored, for example -- but it's a jolly good start