Allow running filaments with system Python interpreter

[rabbitstack]

Fibratus ships with an embedded Python interpreter which facilitates the loading of the Python standard library and interpreter in addition to eliminating the need for users to install the Python distribution separately. Under certain circumstances, it may be beneficial to allow users to use the system interpreter. This could be accomplished by providing a configuration option to specify the root directory of the system Python. Mind it will be necessary to guarantee the Python version Fibratus expects to find matches the version provided by the user.