Symbolic simplification of semidefinite problems

[tcunis]

State-of-the-art sum-of-squares toolboxes offer a simplification of the underlying semidefinite problems prior to calling an SDP solver.

For convex sum-of-squares (or SDP) problems in CaΣoS, simplification should be a two-step process:

1. Symbolic simplification when instantiating a sdpsol object: Simplify the symbolic SDP where possible.
2. Explicit simplification once all parameters and bounds are fixed by the function call.

Ideally, in step 1. we detect where explicit simplification will be needed for step 2.