add sdkgen function to generate pacrom sdk

This generates an android.jar, and then if the build machine has sdk
version 19 installed on it, it will also make a copy of it, and insert
the generated android.jar and create sdk version 219

So using this method, something like OmniGears can be compiled on
Eclipse/Studio without the need of reflection. (The user needs to chose
to compile with sdk 319 instead of sdk 19)

PS1 : Omni -> PAC
PS2 : Commit MSG edited

Change-Id: If08b2aac2e88907e6fdf3b7226ef24b4500ebcc4