Low Power Mode argument for themes

[carloslbello]

Lithium works fine on iOS 9 (besides the preference bundle, which requires an update to PreferenceLoader to work), but does not change the theme if Low Power Mode is enabled. This is because themes do not have a parameter for LPM and Lithium does not check for it. I'm thinking about possibly adding an LPM parameter to themes so that they can look different when it is active. This would require checking the number of arguments a theme function accepts to determine whether it can accept an LPM parameter; existing themes would continue to work unchanged (meaning not having a unique style for LPM). A version of Lithium that does this would be versioned at 2.x and would have the same package ID as usual, so themes that use LPM would need to depend on Lithium >= 2.0.

[carloslbello]

cc @supermamon, this would have implications for the theme editor