Moved parameter IDs to test package

test_design and test_design_space use mostly the same IDs during
testing. These are now defined in __init__.py instead.
On second thought, the parameters that are unique to each test
should probably be defined there as well.
Converted parameter IDs constants to proper naming

All the parameter IDs in __init__.py now follow the standard
global constant naming convention. Updated the design and design
space tests accordingly.
Also added the IDs that were unique to either design or design space
tests to the common definitions.