docker: Include only necessary files in bootstrap image.

The images were getting bloated by vendored files, etc.

.dockerignore

@@ -1,3 +1,7 @@
 Godeps/_workspace/pkg
 Godeps/_workspace/bin
 _test
+java/*/target
+java/*/bin
+php/vendor
+

docker/bootstrap/Dockerfile.common

@@ -67,7 +67,12 @@ ENV CGO_LDFLAGS -L$VTROOT/dist/vt-zookeeper-3.3.5/lib
 ENV LD_LIBRARY_PATH $VTROOT/dist/vt-zookeeper-3.3.5/lib
 
 # Copy files needed for bootstrap
-COPY . /vt/src/github.com/youtube/vitess
+COPY bootstrap.sh dev.env /vt/src/github.com/youtube/vitess/
+COPY config /vt/src/github.com/youtube/vitess/config
+COPY third_party /vt/src/github.com/youtube/vitess/third_party
+COPY tools /vt/src/github.com/youtube/vitess/tools
+COPY travis /vt/src/github.com/youtube/vitess/travis
+COPY php/composer.* /vt/src/github.com/youtube/vitess/php/
 
 # Install gRPC and protobuf as root
 RUN $VTTOP/travis/install_protobuf.sh
@@ -89,3 +94,4 @@ VOLUME /vt/vtdataroot
 
 # If the user doesn't specify a command, load a shell.
 CMD ["/bin/bash"]
+