Remove/hide AndroidAppHelper.createResourcesKey() methods

They are no longer used in XposedBridge, only internally. No module in the
repository used these, there isn't much value of doing so anyway.
Fix delayed configuration update for forwarded resources

addActiveResource() created the ResourcesKey with the current
Configuration in Android 4.2 and higher.
However, this configuration is actually used to override the system
configuration, it should be "null" unless explicitely requested otherwise.

Due to this bug, resource replacements that forward to the module's
resources were loaded with an outdated configuration. For some reason, the
new configuration was applied on the next configuration update, so it was
always one step behind.

Now the system configuration is applied correctly.
More refactoring in AndroidAppHelper

Also, actually use the isThemeable parameter in addActiveResource(), even
though it doesn't seem to be of much value.