Changed framework so all test equip support is performed in one place

Added test_equipment.py in src/test_equipment so that all test equipment
related support is done in one place. Before the developer had to modify
runstp.py to add a test equipment driver into the framework after creating
the driver file. With this change the developer would only have to change
files in src/test_equipment

Signed-off-by: Alejandro Hernandez <ajhernandez@ti.com>