bootstrap/eupsinstall fails to install on python3

PEP-394 posts recommendation as
> The more general python command should be installed whenever any version of Python 2 is installed and should invoke the same version of Python as the python2 command (however, note that some distributions have already chosen to have python implement the python3 command; see the Rationale and Migration Notes below).
> In order to tolerate differences across platforms, all new code that needs to invoke the Python interpreter should not specify python, but rather should specify either python2 or python3 (or the more specific python2.x and python3.x versions; see the Migration Notes).

So, we shall point python3 for bootstrap (currently in ics_config, and proposed to move it into another place - not to put project general script into configuration repository) to get a path for python interpreter.
Also, setup.py in each actor repository have shebang with python, these shall be changed.