Fixes issue for adding Native Library files to APK

Currently the code for include Native Libraries does not work. This pull request fixes the issue.

<H2><b>Here is an example how to added the native libriaries</b></H2>

1)  Add you libraries to the <b>appinventor\lib</b> folder

<b>Example:</b>

	appinventor\lib\sphero\RobotLibrary.jar
	appinventor\lib\sphero\armeabi\libachievement_manager.so
	appinventor\lib\sphero\armeabi-v7ai\libachievement_manager.so



<br>2) In the file <b>appinventor\buildserver\build.xml</b> add the native library

<b>Example:</b>

	<copy toFile="${classes.files.dir}/RobotLibrary.jar" file="${lib.dir}/sphero/RobotLibrary.jar" />
	<copy todir="${classes.files.dir}/armeabi">
		<fileset dir="${lib.dir}/sphero/armeabi" includes="*.so" />
	</copy>
	<copy todir="${classes.files.dir}/armeabi-v7a">
		<fileset dir="${lib.dir}/sphero/armeabi-v7a" includes="*.so" />
	</copy>
    

<br>
3)  In the component file <b>appinventor\components\src\com\google\appinventor\components\runtime\mrSphero.java</b> add the <b>@UsesNativeLibraries</b> annotations as shown below

<b>Example:</b>

	@DesignerComponent(version = 1,
		description = "Component to control Sphero",
		category = ComponentCategory.USERINTERFACE,
		nonVisible = true,
		iconName = "images/mrSphero.png")
	@SimpleObject
	@UsesPermissions(permissionNames = "android.permission.BLUETOOTH_ADMIN, android.permission.BLUETOOTH")
	@UsesLibraries(libraries = "RobotLibrary.jar")
	@UsesNativeLibraries(libraries = "libachievement_manager.so" ,
							v7aLibraries = "libachievement_manager.so")
	public class mrSphero extends AndroidNonvisibleComponent
Is there a reason to remove File.separator from here?