Settings: SlimRecents scaling + lefty mode (3/3)

Squashed:
https://github.com/SlimRoms/packages_apps_Settings/commit/f7a9903d544a63cd93c20fd03588d0eae82aa401
https://github.com/SlimRoms/packages_apps_Settings/commit/64567059877063df91683de0172b108cdfac5a86

    - Add scaling mode....user can scale the overall size down (especially for the
      user with stock dpi requested)

    - Add lefty mode. Recent panel shows up on the left edge instead of the right edge
      for left handed people.

Both are one time accesibility settings. So we put it there.

Change-Id: Ifa7a7299538f3c8f9c592c0c61b48dfa9fbeb2d6

Conflicts:
	res/values/slim_arrays.xml
	res/values/slim_strings.xml
	res/xml/accessibility_settings.xml
	src/com/android/settings/accessibility/AccessibilitySettings.java

Conflicts:
	res/values/strings.xml
	res/xml/general_settings.xml
	src/org/androidx/settings/GeneralSettings.java
OmniGears: make easy to add a checkbox preference

based from Cyanogenmod, but im adding more preferences :D

use SystemCheckBoxPreference if you want adding option for Settings.System
use SecureCheckBoxPreference if you want adding option for Settings.Secure
use GlobalCheckBoxPreference if you want adding option for Settings.Global

example:

we always using like this

    <CheckBoxPreference
        android:key="soft_back_kill_app"
        android:title="@string/soft_back_kill_app_title"
        android:summary="@string/soft_back_kill_app_summary"
        android:persistent="false"/>

and put preference into java code

but with this patch, we can use like this

    <org.omnirom.omnigears.preference.SystemCheckBoxPreference
        android:key="soft_back_kill_app_enable" << put key from android.provider.Settings
        android:title="@string/soft_back_kill_app_title"
        android:summary="@string/soft_back_kill_app_summary" />

the preference will always use presistent command

no need to add this preference into java code again :)
and say goodbye to bad java code style xD

will make all checkbox preference using this, if merged :)

depends on https://gerrit.omnirom.org/#/c/5789/ :)

Change-Id: Ied880d49ccc60c1e02615eccc6d01ddbd30bddf7