Update README.md documentation
Update README.md documentation

Added:
    - Updated feature section list.
    - Added "mnfg" directory description.

Change-Id: Ic4e2cbb474b17491ce1c14ffa82247ee938129f7
Signed-off-by: George Keishing <bef0a9ecac45fb57611777c8270153994e13fd2e@in.ibm.com>

openbmc/openbmc-test-automation,openbmc/openbmc-test-automation