Improve Library usability

[michael-a-hansen]

• [x] slicing for Library instances, so that lib[..., ..., ...] returns a new library with sliced dimensions and properties

• [x] __str__ and __repr__ for Dimension and Library instances to facilitate comprehending a complex library from a black box method (in an interactive environment)

• [x] make library slicing return a view, similarly to numpy - this makes copy semantics the same (since we don't have 'magic' indexing for the library', not yet at least...)

• [x] remove the unstructured dimension capability, that can go back in when there is a clear driver

• [x] enable flamelet and reactor initialization from a library slice

  • [x] consider either writing derived classes of Library for reactors and flamelets (with rethinking extensibility of the library more generally), or, when building a library from reactor or flamelet solvers, include in the extra_attributes dictionary some other things:
  • the abspath of the cantera xml
  • the cantera phase
  • feed/inflow or fuel/oxy TPY/TDY tuples
  • other input arguments to the reactor/flamelet, things like the enthalpy flux switch
  • the nice thing about leveraging extra_attributes is that it's simple and doesn't need more code, the problem is that it's much harder to guarantee anything about it downstream...

[michael-a-hansen]

Commit 1260d32c5d8270620574540d749aed4982371ba3 adds slicing and printing.

[michael-a-hansen]

Commit 35c290e add Library-based Flamelet construction.