Add support to install lithium automatically

[aosen-xiong]

Currently, when start from scratch, and run scripts ./gradlew testDataflowExternalSolvers, the lithium dependency is missing.

Attach is the log:

➜  checker-framework-inference git:(master) ✗ ./gradlew testDataflowExternalSolvers


> Configure project :
====================================
    Checker Framework Inference     
====================================

-------------------------------
Important Environment Variables
-------------------------------
CHECKERFRAMEWORK: /Users/aric/cfi/checker-framework

> Task :testDataflowExternalSolvers FAILED
Buildfile: /Users/aric/cfi/checker-framework-inference/testing/dataflowexample/build.xml

init-libs:

compile-libs:
    [javac] /Users/aric/cfi/checker-framework-inference/testing/dataflowexample/build.xml:22: warning: 'includeantruntime' was not set, defaulting to build.sysclasspath=last; set to false for repeatable builds
    [javac] Compiling 1 source file to /Users/aric/cfi/checker-framework-inference/testing/dataflowexample/libs/bin

BUILD SUCCESSFUL
Total time: 0 seconds

Running DataflowSolver

Traceback (most recent call last):
  File "/Users/aric/cfi/do-like-javac/dljc", line 3, in <module>
    import do_like_javac
  File "/Users/aric/cfi/do-like-javac/do_like_javac/__init__.py", line 1, in <module>
    from . import command
  File "/Users/aric/cfi/do-like-javac/do_like_javac/command.py", line 6, in <module>
    from . import arg
  File "/Users/aric/cfi/do-like-javac/do_like_javac/arg.py", line 13, in <module>
    from . import tools
  File "/Users/aric/cfi/do-like-javac/do_like_javac/tools/__init__.py", line 15, in <module>
    from . import testminimizer
  File "/Users/aric/cfi/do-like-javac/do_like_javac/tools/testminimizer.py", line 8, in <module>
    import lithium
ModuleNotFoundError: No module named 'lithium'

FAILURE: Build failed with an exception.