Add CLI option support to Scala.js partest interface

The following options are now supported (and replace the corresponding
environment properties). Note that they are mutually exclusive.

    --blacklisted      Run blacklisted tests only
    --buglisted        Run buglisted tests only
    --whitelisted      Run whitelisted tests only
    --unknown          Run unknown tests only
    <name> ...         Run exactly these tests

A couple of usage examples:

    sbt> scalajs-partest-suite/testOnly -- --unknown
    sbt> scalajs-partest-suite/testOnly -- run/amp.scala run/t1466.scala
Add MemVirtualWriters
Remove dependency on lift-json. Introduce JSON helpers
Fix #456: Run partest with fastOpt and Node.js

This adds the following options to the partest runner:

    --noOpt      Don't optimize, use Rhino (default)
    --fastOpt    Run DCE and run with Node.js

These options can be combined with the test selectors. Example usages:

    sbt> scalajs-partest-suite/testOnly -- --fastOpt
    sbt> scalajs-partest-suite/testOnly -- --fastOpt --unknown
    sbt> scalajs-partest-suite/testOnly -- --fastOpt run/amp.scala run/t1466.scala