Add a vision pins wrapper for legacy API usage
Add a vision pins wrapper for legacy API usage

Prints a message to upgrade, but ultimately just imports from
aiy.pins to allow user to proceed.

Change-Id: Ie74c0297ed011b18621b20f1d253025995dba959

google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian