testsdkext: Add skeleton for support Extensible SDK tests.
oeqa/sdkext: Add module and __init__.py will contain eSDK tests.
classes/testsdk: Add support for run eSDK tests.
oeqa/oetest: Create oeSDKExtTest for now only inherit oeSDKTest,
modified SDKExtTestContext now inherit SDKTestContext
and set sdkext filesdir for store data fixtures.
Signed-off-by: Aníbal Limón <limon.anibal@gmail.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
