add "make path third_party_core" support in gradle

In these commits:
1. we add task compileThirdPartyLibraries in build.gradle, which invokes "make path third_party_core" in building process.
2. we add a function to setup the account of SSH in our demo program.
3. we have simplified the configuration of host file.
4. gradle will skip those object files in src directory,

Note: As the PS libraries generated by gradle and the original makefile are slightly different,  so gradle will not link any existed PS libraries in "lib" and the building process of gradle is totally independent to the original make system. It's not necessary to run "make clean" before "gradle build"