Allow additional control as to which tests are run
Allow additional control as to which tests are run

Supplying a path to the tests spec file, now allows one to run
only the tests supplied in that tests file:

./run_tests --spec-file tests/kernels/simple_diffusion/tests
      OK kernels/simple_diffusion.test
-----------------------------------------------------

Or by providing a directory containing the tests file:

./run_tests --spec-file tests/kernels/simple_diffusion
      OK kernels/simple_diffusion.diffusion_200x200
      OK kernels/simple_diffusion.diffusion_100x100
      OK kernels/simple_diffusion.uniform_refine_4
      OK kernels/simple_diffusion.test
-----------------------------------------------------

You can further alter the search logic with -i (and --re) accordingly:

./run_tests --spec-file tests/kernels/simple_diffusion -i speedtests
      OK tests/kernels/simple_diffusion.diffusion_200x200
      OK tests/kernels/simple_diffusion.uniform_refine_4
      OK tests/kernels/simple_diffusion.diffusion_100x100
-----------------------------------------------------

Closes #11076

laagesen/moose,nuclear-wizard/moose,dschwen/moose,milljm/moose,sapitts/moose,sapitts/moose,dschwen/moose,permcody/moose,laagesen/moose,sapitts/moose,harterj/moose,laagesen/moose,lindsayad/moose,bwspenc/moose,sapitts/moose,andrsd/moose,sapitts/moose,YaqiWang/moose,jessecarterMOOSE/moose,andrsd/moose,harterj/moose,dschwen/moose,YaqiWang/moose,dschwen/moose,SudiptaBiswas/moose,idaholab/moose,lindsayad/moose,milljm/moose,harterj/moose,jessecarterMOOSE/moose,permcody/moose,bwspenc/moose,YaqiWang/moose,SudiptaBiswas/moose,andrsd/moose,idaholab/moose,permcody/moose,lindsayad/moose,YaqiWang/moose,nuclear-wizard/moose,idaholab/moose,SudiptaBiswas/moose,milljm/moose,permcody/moose,idaholab/moose,dschwen/moose,SudiptaBiswas/moose,bwspenc/moose,jessecarterMOOSE/moose,SudiptaBiswas/moose,lindsayad/moose,harterj/moose,laagesen/moose,andrsd/moose,nuclear-wizard/moose,milljm/moose,nuclear-wizard/moose,jessecarterMOOSE/moose,idaholab/moose,milljm/moose,lindsayad/moose,andrsd/moose,bwspenc/moose,bwspenc/moose,jessecarterMOOSE/moose,harterj/moose,laagesen/moose