Adds support for the New Relic module's compile time dexer agent.

New Relic for Android requires an additional argument to be passed to the Android SDK dx command when it is invoked at compile time. This PR looks for the New Relic Titanium module and if present, appends an argument to the dexer so that New Relic instrumentation occurs.

The file passed to the dexer is a temporary file. This is because the dex argument does not like spaces in the filename, and under OSX at least the module directory is very likely to have spaces in it, due to 'Application Support' etc. The temporary file is cleaned up automatically after the dexing phase is done.