Update makefile to add $JAVA_HOME/include/linux to JAVA_INCLUDES on Linux
made a few changes to pull request #2:

instead of linking to objects files directly on the build directory,
we do run the install target of external makefiles, but locally without sudo.
Merge branch 'tal-m-master'
Merge pull request #3 from ddunwoody/add_jni_include_linux

Update makefile to add $JAVA_HOME/include/linux to JAVA_INCLUDES on Linu...
Update submodule remotes to use HTTPS URLs

Author:    David Dunwoody <david.dunwoody@gmail.com>
Update .gitignore to ignore generated files in install/* and IntelliJ IDEA files
Update makefile's clean target to delete files copied to assets/ and the install dir
Add Maven build as convenience for installing to a Maven repo (not used in makefile)