This CL mainly changes:
1. Add 2 new FE modules
1. fe-common
save all common classes for other modules, currently only `jmockit`
2. spark-dpp
The Spark DPP application for Spark Load. And I removed all dpp related classes to this module, including unit tests.
2. Change the `build.sh`
Add a new param `--spark-dpp` to compile the `spark-dpp` alone. And `--fe` will compile all FE modules.
the output of `spark-dpp` module is `spark-dpp-1.0.0-jar-with-dependencies.jar`, and it will be installed to `output/fe/spark-dpp/`.
3. Modify some bugs of spark load
