Enhance themeing logic

[designmatty]

1: replace entries in derived with values from base (newDerived)
2: merge derived into blaster base theme (newBase)
3: pull out user base theme (userBase)
4: pull out user component theme (userComps)
5: Replace entries in (step3/userBase) with valuse from (Step 2/newBase) (newUserBase)
6: merge (step 5/newUserBase) into (step 2/newBase) output (combinedBase)
7: merge (step4/userComps) into blaster components (newComps)
8: replace entries in (step4/userComps) with values from (step 6/combinedBase) (newUserComps)
9: merge (step 7/newComp)s output into (step 8/newUserComps)s output (combinedComps)
10: merge (step 9/combinedComps) with (step 6/combinedBase)

Utilize this codesandbox for testing: https://codesandbox.io/s/blaster-utility-testing-env-c6sfy