* Adds .java-version to specify Java 1.7 as the JDK version to use
for CloudStack development.
* Adds .python-vresion to specify Python 2.7.11 as the Python to
use for CloudStack development.
* Adds requirements.txt to specify the default dependencies used
for CloudStack development. It does not include Marvin's
dependencies because it's bundle already defines the dependencies
which are installed with Marvin.
* Adds .java-version and .python-version to the RAT excludes
because neither jenv or pyenv support comments in these files
* Updates INSTALL.md to explain how to utilize jenv and pyenv for
CloudStack development
