Introduction of a tool to find main dex classes.

This is for legacy application wanting to allow --multi-dex on dx
and load the multiple files using the com.android.multidex.installer
library. The mainDexClasses script will provide the content of the
file to give to dx in --main-dex-list.

Change-Id: Id14bc785c6a888f6af49c018b2c29b89284ae40e
11 files changed