Isofit

This is a minor upgrade to ensure that lookup table files are always given consistent names across multiple runs. This enables re-using and sharing of precalculated lookup tables.

-Enables coupled VSWIR TIR inversions
-Brings in substantial multicore speedups
-Removes numba
-General code improvements and stability
-Configuration radiative transfer file format has been modified slightly, and are no longer strictly backwards compatible with v1.*

New faster, stable matrix inversions courtesy Jouni Susiluoto
Removed vestigial VectorInterpolatorJIT code
Fixed a recently-introduced array indexing issue in multidimensional lookup tables

* Closes PR 62
* Includes a small change to the VectorInterpolator class that dramatically improves its performance (~15x)
* Closes PR 63
* Minor bug fixes

Surface reflectance partial derivatives: Incorporates a small but important fix to some partial derivative calculations in the radiative transfer codes.

* Closes PR 55:
* Predicts high-resolution reflectance uncertainty based on the RSS of per-spectrum instrument noise and radiometric calibration uncertainty

* Closes PR 49:
* Adds global jit_enabled flag (defaults to False) to conditionally enable jit compilation.
* Adds global warnings_enabled flag
* Corrects the ISOFIT cli command so that it imports isofit.core.isofit and runs within a try-except, rather than defining it separately
*

* Tweaks to example code to remove calls to "run()".