Add API entry and validation checks(GLES 3.1 section 7.3).
Add the first 4 interfaces(PROGRAM_INPUT, PROGRAM_OUTPUT,
UNIFORM and UNIFORM_BLOCK) implementation.

BUG=angleproject:1920
TEST=angle_end2end_tests:ProgramInterfaceTestES31.*

Change-Id: Iab80ba332e2a5e2b3e677039359e60a420e3d6b0
Reviewed-on: https://chromium-review.googlesource.com/642729
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>