Add the ability to turn off dependency locking

This makes it easy to experiment with new dependency versions or new plugins
without having to update the lock files, by adding "-PdisableDependencyLocking=true" to any gradle command.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=249463575

gradle/build.gradle

@@ -1,8 +1,10 @@
 buildscript {
+  if (project.disableDependencyLocking.toBoolean() == false) {
     // Lock buildscript dependencies.
     configurations.classpath {
       resolutionStrategy.activateDependencyLocking()
     }
+  }
 
   dependencies {
     classpath 'com.google.cloud.tools:appengine-gradle-plugin:1.3.3'
@@ -98,17 +100,19 @@ subprojects {
   // Skip no-op project
   if (project.name == 'services') return
 
+
+  if (rootProject.disableDependencyLocking.toBoolean() == false) {
     buildscript {
       // Lock buildscript dependencies.
       configurations.classpath {
         resolutionStrategy.activateDependencyLocking()
       }
     }
-
     // Lock application dependencies.
     dependencyLocking {
       lockAllConfigurations()
     }
+  }
 
   def services = [':services:default',
                   ':services:backend',

gradle/buildSrc/build.gradle

@@ -1,8 +1,10 @@
 buildscript {
+  if (rootProject.disableDependencyLocking.toBoolean() == false) {
     // Lock buildscript dependencies.
     configurations.classpath {
       resolutionStrategy.activateDependencyLocking()
     }
+  }
 }
 
 plugins {
@@ -17,9 +19,11 @@ plugins {
   id 'com.diffplug.gradle.spotless' version '3.18.0'
 }
 
-// Lock application dependencies.
-dependencyLocking {
+if (rootProject.disableDependencyLocking.toBoolean() == false) {
+  // Lock application dependencies.
+  dependencyLocking {
     lockAllConfigurations()
+  }
 }
 
 repositories {

gradle/buildSrc/gradle.properties

@@ -0,0 +1 @@
+disableDependencyLocking=false

gradle/gradle.properties

@@ -4,3 +4,4 @@ uploaderDestination=
 uploaderCredentialsFile=
 uploaderMultithreadedUpload=
 flowDocsFile=
+disableDependencyLocking=false