Add a partially java compatible shell.

[brendandahl]

Makes it much easier to compare output to hotspot from the command line and makes it possible to easily switch between node and spidermonkey.

Changes from the current shell:

• tests.jar and benchmark.jar are no longer automatically included you'll need to add it to the class path js shell/pluot.js -cp bench/benchmark.jar benchmark.InvokeVirtual
• options are now more like java where a ':' separator is used e.g. flag is now -w:jc
• -jar option was added so it is now possible to run a jar that has the main class in the manifest file
• Node uses the same file so just exchange the above js for node

Maybe future work:

• The classpath support still needs some work to support directories and not just jar files to match java.
• Remove the default of printing stats
• Remove message from emscripten about "pre-main prep time: 0 ms"

[mbebenita]

:+1: