Modernize Android build system, bump dependencies

Summary:
- Build against Android SDK 26
- Upgrade to Gradle 4
- Upgrade to Android Plugin 3.0, adjust dependency management accordingly
- Upgrade Maven deployment plugin

Reviewed By: emilsjolander

Differential Revision: D6272007

fbshipit-source-id: b198b4c8e1a94e2ee031ad26193fdfdf5b52adf1

build.gradle

@@ -3,11 +3,12 @@
 buildscript {
     repositories {
         jcenter()
+        maven { url 'https://maven.google.com/' }
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.3.3'
+        classpath 'com.android.tools.build:gradle:3.0.0'
         classpath 'com.jfrog.bintray.gradle:gradle-bintray-plugin:1.7.3'
-        classpath 'com.github.dcendents:android-maven-gradle-plugin:1.5'
+        classpath 'com.github.dcendents:android-maven-gradle-plugin:2.0'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
@@ -23,8 +24,8 @@ allprojects {
 ext {
     minSdkVersion = 14
     targetSdkVersion = 25
-    compileSdkVersion = 25
-    buildToolsVersion = '25.0.2'
+    compileSdkVersion = 26
+    buildToolsVersion = '26.0.2'
     sourceCompatibilityVersion = JavaVersion.VERSION_1_7
     targetCompatibilityVersion = JavaVersion.VERSION_1_7
 }