main: Move graphyte_main.py to graphyte/main.py

Originally we use graphyte_main.py as the entrance script. Now we
change to use 'python -m graphyte.main' to execute it, then we can
avoid considering the path of the script, especially when we install
it at Windows platform.

BUG=none
TEST=make test; make lint

Change-Id: If4281b1d18dd800cc63bd3e8066cd0d3074aacac
2 files changed