Removed Container, Linker and other classes from theano package

Always import config from configdefaults directly

A small step towards not importing theano from within the codebase.
closes #234

Rename and rearrange imports

Fixes a performance digression caused by Blas Ops that did not leverage C-thunking.

The CLinkerOp and CLinkerObject like types were moved into link.c.interface to get them out of gof.
PureOp and Op were merged (as Op) which means that some C-related methods are now declared on all Ops.

+ BITWIDTHs are now constants in utils.
+ Lambdas and local functions for default/filter/validate are now module-level local functions. This fixes pickleability (closes #240).

Move linkers to link module

The `CVM` class definition was also split off into `theano.link.c.cvm`.