Split protobuf into its own project

We don't want core to depend on protobuf.

compiler/build.gradle

@@ -21,8 +21,8 @@ executables {
 }
 
 dependencies {
-  compile project(':grpc-stub'),
-          libraries.protobuf
+  testCompile project(':grpc-protobuf'),
+              project(':grpc-stub')
 }
 
 binaries.all {

core/build.gradle

@@ -5,8 +5,7 @@ plugins {
 description = 'gRPC: Core'
 
 dependencies {
-    compile libraries.protobuf,
-            libraries.guava,
+    compile libraries.guava,
             libraries.jsr305
 }
 

examples/build.gradle

@@ -15,7 +15,7 @@ buildscript {
 dependencies {
     compile project(':grpc-core'),
             project(':grpc-netty'),
-            project(':grpc-okhttp'),
+            project(':grpc-protobuf'),
             project(':grpc-stub'),
             libraries.jsonp
 }

integration-testing/build.gradle

@@ -21,6 +21,7 @@ dependencies {
     compile project(':grpc-core'),
             project(':grpc-netty'),
             project(':grpc-okhttp'),
+            project(':grpc-protobuf'),
             project(':grpc-stub'),
             project(':grpc-testing'),
             libraries.junit,

protobuf/build.gradle

@@ -0,0 +1,7 @@
+description = 'gRPC: Protobuf'
+
+dependencies {
+    compile project(':grpc-core'),
+            libraries.protobuf,
+            libraries.guava
+}

settings.gradle

@@ -3,6 +3,7 @@ include ":grpc-core"
 include ":grpc-stub"
 include ":grpc-auth"
 include ":grpc-okhttp"
+include ":grpc-protobuf"
 include ":grpc-nano"
 include ":grpc-netty"
 include ":grpc-testing"
@@ -16,6 +17,7 @@ project(':grpc-core').projectDir = "$rootDir/core" as File
 project(':grpc-stub').projectDir = "$rootDir/stub" as File
 project(':grpc-auth').projectDir = "$rootDir/auth" as File
 project(':grpc-okhttp').projectDir = "$rootDir/okhttp" as File
+project(':grpc-protobuf').projectDir = "$rootDir/protobuf" as File
 project(':grpc-nano').projectDir = "$rootDir/nano" as File
 project(':grpc-netty').projectDir = "$rootDir/netty" as File
 project(':grpc-testing').projectDir = "$rootDir/testing" as File