Filter Scala-related noise from JaCoCo results

Adds a new "format", `ScalaHTMLReport` that hides instruction and
branch coverage from the tabular views. These are too noisy primarily because
of synthetic null checks that scalac adds around calls to `==` and `##`
and in the constructors of classes with `$outer` parameters.

Pattern matching is also likely to generate more branches than are tested
in many cases, so its not clear if this will be an easy feature to reenable.

Install a custom `ClassAnalyzer` that omits some methods from
   the reports, namely:
     - simple accessors
     - trait forwarders
     - static forwarders
     - extension method forwarders
     - implicit class factories
     - generated case class and AnyVal methods

This is all something of a stopgap solution until JaCoCo offers a richer
API for filtering, which is being discussed for Q1 2014.
Merged in retronym/jacoco4sbt/topic/scala-awareness (pull request #4)

Filter Scala-related noise from JaCoCo results
added option to display branch coverage in new Scala report, converted Java to Scala, fixed ScalaDoc warning, misc small other cleanup
updated to 2.1.2
Added tag 2.1.2 for changeset 0a8d9f1cc83d
hgignore -> gitignore
added comment headers