Export function to show assertions.

This is necessary to name test cases for #48.
Implement monad transformers for computations with embedded assertions.
Run source files with assertions as unit tests (fix #48).
Merge pull request #54 from Toxaris/topic/assertions-as-tests

Run assertions as tests
Reorganize module hierarchy PTS.Syntax.*.

The new module PTS.Syntax exports everything the other modules of the
system need to know about the syntactic structure of PTS programs,
including the AST datatypes and support for folding, parsing, pretty
printing and substitution. These features are implemented in the
modules of the PTS.Syntax.* hierarchy. Fixes #34.
Split PTS.Syntax.AST.
Format list of exposed modules.

The list is now ordered alphabetically. List items are no longer
separated by commas to reduce diff noise when adding at the end
of the list.
Reorganize module hierarchy PTS.Dynamics.*.

The new module PTS.Dynamics exports everything the other modules of the
system need to know about the dynamic semantics of PTS programs,
including the Value type and support for evaluation, reification,
Normalization and  comparision of values. These features are implemented
in the modules of the PTS.Dynamics.* hierarchy.
Reorganize module hierarchy PTS.Statics.*.

The new module PTS.Statics exports everything the other modules of the
system need to know about the static semantics of PTS programs,
including support for type checking. These features are implemented
in the modules of the PTS.Statics.* hierarchy.
Delete unused files.
Reorganize tests for PTS.Syntax.*.

Realign the names of test modules with the names of the modules
under test.
Reexport from PTS.Syntax explicitly and by name.

Benefits of explicit reexports: The haddock documentation mentions
all exported binding, we can structure the haddock documentation,
and we can reexport only a subset of the imported bindings.
Organize imports.

Sort alphabetically, and remove some unused imports.
Delete empty module.
Remove old code.

The code was commented-out for quite some time.
Move Errors monad to Control.Monad.*.
Reorganize module hierarchy PTS.Process.*.

The new module PTS.Process exports everything the other modules of the
system need to know about processing *.lpts and *.pts files.
Inline Parametric.AST into PTS.Syntax.Names.
Add examples about Church numerals (see #21).
Avoid non-ASCII characters.

This is a work-around for #59.