[Android] Implement OnSharedPreferenceChangeListener within PrefsActivity.java. This allows us to immediately save to the ini config when a preference in the front-end is changed, rather than waiting for the settings window to close. This also allows us to remove handling for preferences from CPUSettingsFragment.java and VideoSettingsFragment.java.
Remove some unnecessary includes.
Revert "Remove some unnecessary includes."

Turns out this explodes on Linux.

This reverts commit c4696568cc15d140cbdae460cd5e227c46845114.