Default some COFFEE optimizations to on
Set default optimization level
Change coffee's modules names
Merge pull request #375 from firedrakeproject/fix-coffee-imports

* fix-coffee-imports:
  Change coffee's modules names
Bump version to 0.12.0

Also adapt ffc compatibility version.
Merge pull request #370 from firedrakeproject/turn-on-coffee-opts

* turn-on-coffee-opts:
  Set default optimization level
  Default some COFFEE optimizations to on
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Dispatch on C/Python Expressions based on "eval" attribute

It's not safe to check for a .code attribute in an Expression and assume
it's a "C kernel" one, since the user may have subclassed expression and
called the superclass __init__ method.  Instead, check for eval and
assume that if it exists we have a Python Expression.