oeqa/core/context: Add support of OETestContextExecutor
The OETestContextExecutor class supports to use oe-test for run core
test component also is a base class for the other test components
(runtime, sdk, selftest).
Te principal functionality is to support cmdline parsing and execution
of OETestContext, the test components could extend the common options
to provide specific ones. The common options between test components
are test data file, output log and test cases path's to scan.
Also it initializes the logger to be passed to the whole OEQA framework.
