Refactor implementation of Scheme derived expressions

The method to register and to detect Scheme derived expressions has
become simplier, more flexible, and more easily extensible.  Similiar
to the scheme library mechanism, the set of derived expressions are
now registered with and found using a "syntactic" environment during
Scheme code analysis.  This refactoring of the implementation is a
first step towards implementing a Scheme macro system.

The CSCM roadmap has been modified to raise the priority of the Scheme
macro system and lower the priority of the Scheme numeric tower.
Rename subset of Erlang types

Rename subset of Erlang types to better distinguish between types used
for Scheme (static) code analysis and types used for Scheme (dynamic)
code evaluation.
Update rebar (2.1.0-pre-143-g8b667f1)
Refactor implementation of Scheme derived expressions

The process of scanning out internal definitions should only be done
if the implementation of 'define' and 'define-values' registered in
the "syntatic" environment matches with the corresponding builtin
implementations.
Use fully qualified fun syntax for Scheme library exports
Minor refactorings and cleanups based on code review