Add new manifest option for install location

Add new manifest option for install location
Change recommendAppInstallLocation api
add code to parse new attribute.
Define flags in PackageInfo
Add new settings attributes for enabling setting and value for install location
Some tests
The policy for install location: if explicitly set in manifest as internal only we try to install the app only on internal storage. if set to preferExternal, we try to install it on sdcard if possible. If not we fall back to internal.
If the user enables setting SET_INSTALL_LOCATION(which will always
be set to false in final release builds) and sets a prefered location, we try
to honour it.