Add solver support for point-wise Riemann solvers

Also adds acoustics example and test
Fix function signature indentation
Add point-wise tets correctly
Add 2d point-wise example and test
Merge pull request #473 from mandli/ptwise-support

Add solver support for point-wise Riemann solvers

This adds tests for the new pointwise solvers, and extends the code that automatically detects num_waves, num_eqn to work with the pointwise solvers.