Added a .gitignore to TestCases/ to avoid adding mesh/solution data to the SU2 repo.
Added a .gitignore to TestCases/ to avoid adding mesh/solution data to the SU2 repo.

jlabroquere/SU2,pawhewitt/Dev,drewkett/SU2,hlkline/SU2,srange/SU2,KDra/SU2,Heathckliff/SU2,jlabroquere/SU2,opfeifle/SU2,kulkarnimandar/SU2,cspode/SU2,bankur16/SU2,jlabroquere/SU2,jlabroquere/SU2,cspode/SU2,KDra/SU2,Heathckliff/SU2,kulkarnimandar/SU2,bankur16/SU2,KDra/SU2,jlabroquere/SU2,Heathckliff/SU2,srange/SU2,kulkarnimandar/SU2,Heathckliff/SU2,opfeifle/SU2,cspode/SU2,hlkline/SU2,KDra/SU2,pawhewitt/Dev,cspode/SU2,drewkett/SU2,srange/SU2,opfeifle/SU2,kulkarnimandar/SU2,bankur16/SU2,Heathckliff/SU2,bankur16/SU2,hlkline/SU2,pawhewitt/Dev,opfeifle/SU2,pawhewitt/Dev,bankur16/SU2,cspode/SU2,kulkarnimandar/SU2,pawhewitt/Dev,srange/SU2,cspode/SU2,opfeifle/SU2,Heathckliff/SU2,bankur16/SU2,hlkline/SU2,hlkline/SU2,pawhewitt/Dev,KDra/SU2,drewkett/SU2,drewkett/SU2,jlabroquere/SU2,drewkett/SU2,opfeifle/SU2