Fixes issue in https://github.com/freechipsproject/rocket-chip/pull/848

* Fixed inability to disable combo loop check
Moved checking of dontCheckComboLoops into loadAnnotations so
that it works in cases where Driver.execute is not used.

* Fix test for annotations, modifications to loadAnnotations
made 2 more annotations visible.

* Remove debug println from DriverSpec

Const prop regs

Preserve "better" names in Constant Propagation

Names that do not start with '_' are "better" than those that do

Use Travis Build Stages

Improvements to Constant Propagation and Testing

Constant Propagation will not optimize across components marked
dontTouch

This makes it more concise to write tests

Gives all transform specs access to useful utilities (like dontTouch).
Deletes some duplicate code. Parsing mode UseInfo is fine for
everything, only matters if the test actually uses info.

Remove reset and fix bug in register update Verilog emission

Fixes bug where the Verilog emitter could pull the next value for a
register that feeds a second register, removing the first register from
the second register's update.

This requires a quick second pass to back propagate constant wires but
the QoR win is substantial. We also only need to count back propagations
in determining whether to run ConstProp again which shaves off an
iteration in the common case.

Similar to #543

Also add tests for what should happen to 'is invalid' in ExpandWhens
Fixes #606

Resolves #600

* Display the total time firrtl took to compile
* Switch timing print out to error(aka default)

Makes Verilog more readable to both humans and scripts

* Update dependencies and JavaConverters for Scala 2.12

* Bump Scala (and library) version(s).

* replace "error" with "Utils.error"; bump Scala version to 2.11.11

We walked the whole set of vertices for every dont touch

We were recursing on Types of Expressions which not only is super inefficient
(especially since we are already calling InferTypes afterward), but also
duplicates each of the Type objects that need changing.