unix/main: Update stdlib path envvar (now PYCOPYPATH) and its default value.
unix/main: Update stdlib path envvar (now PYCOPYPATH) and its default value.

To avoid possible confusion and mix-up between Pycopy and MicroPython
installs. The environment variable is now PYCOPYPATH, and default value
of the search path is "~/.pycopy/lib:/usr/lib/pycopy".

Change-Id: I517d762a0d7b4a6fcf3edb3d9c30fb8c59c40e98
Signed-off-by: Paul Sokolovsky <9dc5061f178bb11813e14f1ed02ba27eaf21fa5d@users.sourceforge.net>

pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython