Add eclipse plugin to gradle.build

[shvachko]

See pull requested. Tested it with my Eclipse. Just run $./gradlew eclipse

[pjeli]

Unfortunately this patch breaks the build for us without Eclipse:

LM-SJN-00877839:giraffa pljeliazkov$ ./gradlew clean build
....
/Users/pljeliazkov/workspace/giraffa/giraffa-core/build/generated/java/org/apache/giraffa/GiraffaProtos.java:9: error: package com.google.protobuf does not exist
      com.google.protobuf.ExtensionRegistry registry) {
                         ^
/Users/pljeliazkov/workspace/giraffa/giraffa-core/build/generated/java/org/apache/giraffa/GiraffaProtos.java:2308: error: package com.google.protobuf.Descriptors does not exist
  private static com.google.protobuf.Descriptors.Descriptor
                                                ^
/Users/pljeliazkov/workspace/giraffa/giraffa-core/build/generated/java/org/apache/giraffa/GiraffaProtos.java:2311: error: package com.google.protobuf.GeneratedMessage does not exist
    com.google.protobuf.GeneratedMessage.FieldAccessorTable
                                        ^
....
FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':giraffa-core:compileGeneratedJava'.
> Compilation failed; see the compiler error output for details.
....
BUILD FAILED
....

[pjeli]

It seems ./gradlew clean assemble works fine. But when I try to run clean build I get the failures. @milandesai, do you see the same thing?

[shvachko]

I did clean test, which works. But you are right clean build doesn't. It breaks on compileGeneratedJava. Checking now.

[shvachko]

Updated PR. Both clean build and eclipse targets work for me.

[shvachko]

The last update is to make it work with gradle 3.

[pjeli]

+1 -- Works for me!

[shvachko]

Committed