Collect an overview of uflacs optimisations

[Martin Sandve Alnæs]

At the moment the focus on uflacs development is on getting to feature completeness.

Collecting optimisation ideas here for later prioritization and implementation.

Possible adjustments more on the FFC side:

• Remove unused psi tables.

Generic code generation improvements:

• Handle conditionals properly with if-else blocks

Partitioning and scheduling algorithms:

• Improve cost heuristics.
• Split up typical huge line at end of code generation.

Algorithm tuning:

• Expose uflacs code generation parameters for experimentation.
• Automate search for optimal code generation parameters.

More ideas are found as comments in the code, collect them here later by looking through the code.

[Martin Sandve Alnæs]

Not very interesting comments in here. Will rather open new issues for each significant optimization.