Change bazel-genfiles to bazel-bin as per Bazel 0.25

In Bazel 0.25, the bazel-genfiles isn't used anymore as target
directory. Everything, including plugins, is generated into bazel-bin.

Change-Id: I9521cd7e572ece855cfa79841fcd0b066857fe04
diff --git a/Documentation/dev-bazel.txt b/Documentation/dev-bazel.txt
index 37ed9ac..3cbb609 100644
--- a/Documentation/dev-bazel.txt
+++ b/Documentation/dev-bazel.txt
@@ -75,7 +75,7 @@
 Java docs will be placed in:
 
 ----
-  bazel-genfiles/api.zip
+  bazel-bin/api.zip
 ----
 
 Install {extension,plugin,gwt}-api to the local maven repository:
@@ -99,13 +99,13 @@
 The output JAR files for individual plugins will be placed in:
 
 ----
-  bazel-genfiles/plugins/<name>/<name>.jar
+  bazel-bin/plugins/<name>/<name>.jar
 ----
 
 The JAR files will also be packaged in:
 
 ----
-  bazel-genfiles/plugins/core.zip
+  bazel-bin/plugins/core.zip
 ----
 
 To build a specific plugin:
@@ -117,7 +117,7 @@
 The output JAR file will be be placed in:
 
 ----
-  bazel-genfiles/plugins/<name>/<name>.jar
+  bazel-bin/plugins/<name>/<name>.jar
 ----
 
 Note that when building an individual plugin, the `core.zip` package