Architecture decisions

Short records of decisions that shape fitwise. Each one states the context, the decision and its consequences. New decisions get the next free number; superseded ones stay and link to their replacement.

• 1. License: BSD-3-Clause
• 2. Orthogonal distance regression via odrpack
• 3. Covariance convention
• 4. Documentation with Sphinx and sphinx-gallery
• 5. Nonlinear solver: scipy.optimize.least_squares with normalization and restarts
• 6. Direct solution of linear models
• 7. Starting values for user functions: multi-start with variable projection