first test to add a gradle local dependency
remove android-passcodelock for now
use android-passcodelock as a local dependency
use maven central repo for some old packages
Merge branch 'develop' into issue/1423-gradle-local-dependencies

Conflicts:
	build.gradle
use mixpanel-android provided by maven central
add git submodule commands to the readme
Moved to gradle multiproject build structure
Add comment to top level build.gradle
Merge branch 'issue/1423-gradle-local-dependencies' of github.com:wordpress-mobile/WordPress-Android into issue/gradle-structure

Merges #1423

`com.mixpanel.android:mixpanel-android:4.2.1` is missing:

`com.mixpanel.android.mpmetrics.MixpanelAPI`

Conflicts:
	WordPress/libs/MixpanelAPI.jar
	build.gradle
	settings.gradle
Using aar artifact for mixpanel
Merge branch 'develop' of github.com:wordpress-mobile/WordPress-Android into issue/gradle-structure

Conflicts:
	build.gradle
Updating gson to 2.2.4
Reverting to gson 2.2.2

`StringMap` is no longer available.

> Replaced by LinkedHashTreeMap.

https://groups.google.com/forum/#!topic/google-gson/hRi8Vqc9xLg
fix the output directory where crashlytics.properties is generated