Hide the AM/PM preference completely if using a 24-hour clock

In addition, this commit also fixes a bug where the switch would not be
disabled on a fresh 24-hour clock install, as the preference value would
be null. This is avoided by using a higher-level method from
DateFormat to check the clock mode.

Patch Set 2: improve code styling

Patch Set 3: remove pointless application context retrieval

Change-Id: I80de938df61803649688723843439905e9909b07
Settings: ES translations

- Rotate lock screen
- Minor changes

Change-Id: Ia493de6b30315e695072d92a6ddef9c4f250e4ba
Merge "Settings: ES translations" into cm-10.1
Merge branch 'cm-10.1' of git://github.com/CyanogenMod/android_packages_apps_Settings into cm-10.1

Revert "Hide the AM/PM preference completely if using a 24-hour clock"
http://review.cyanogenmod.org/#/c/45938/