Vine: Support more thread limits.

[dthain]

Proposed changes

Add environment variables to control thread quantity for MKL, VECLIB, BLAS, and NUMEXPR, in addition to the existing OpenMP. Numpy and other systems may use any or all of these depending on how they were compiled.

Post-change actions

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• make test Run local tests prior to pushing.
• make format Format source code to comply with lint policies. Note that some lint errors can only be resolved manually (e.g., Python)
• make lint Run lint on source code prior to pushing.
• Manual Update Did you update the manual to reflect your changes, if appropriate? This action should be done after your changes are approved but not merged.
• Type Labels Select github labels for the type of this change: bug, enhancement, etc.
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• PR RTM Mark your PR as ready to merge.

Additional comments

This section is dedicated to changes that are ambitious or complex and require substantial discussions. Feel free to start the ball rolling.

[btovar]

The nice thing about standards is that you have so many to choose from.

[btovar]

Ready to merge?

[dthain]

RTM