Implement a proper API to conveniently use MuSink core

Currently, one has to manually step through workspaces. Create user-friendly APIs that automate several common tasks. Desired features:

• create and solve problems without explicitly handling nodes (provide reliable API that uses indices)
• eps scaling
• automatic switch to logdomain if the expdomain-potentials diverge
• allow for transparent mass or sharpness targets / constraints instead of specifying rho and eps