Lockscreen: See through (2/2)

Add the ability to see through lockscreen.
Adapted to kitkat from jellybean by @BigBrother1984

Signed-off-by: D4rKn3sSyS <jesdga95@gmail.com>
Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>

PS2:

* Indenting and fix of the LOCKSCREEN_SEE_THROUGH variable check.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>

PS3:

* Add see through checkbox to security_settings_chooser.xml, reflects the security_settings_lockscreen.xml.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>

PS4:

* Made the option available with every lock mode (PIN, Password etc.) cause it works with every mode now.
* Update description with better one.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>

PS5:

* Make description more like aosp strings.

Change-Id: I8c8d70d214bc36504ff0cfbe8d40656eb56d62ff
Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>