Remove outflow boundary condition diode for MHD

[bcaddy]

Disable diode outflow boundaries for MHD

Since MHD needs a larger stencil the diode in the outflow BC's was causing issues. After discussion with @evaneschneider the diode has been disabled for MHD builds.

Clang Tidy

Minor tweaks to fix clang-tidy's readability-qualified-auto and clang-analyzer-optin.cplusplus.UninitializedObject checks.

The readablity check was fixed by commenting out some currently used code, it's not deleted since it will be used again when MHD is finished; at which time the actual error will be fixed.

The clang-analyzer check was fixed by initializing some member variables in the OneTime class. @alwinm, I'd like you to take a look at this and make sure I haven't broken anything.

Other

• Switched more indexing over to using grid_enums and added enums for the CT electric fields.
• Cleaned up the arguments for the HLLD solver, removed unused ones, etc[
• Fix issues with Dai & Woodward shock tube initial conditions
• Up the size of all MHD shock tubes from 32^3 to 64^3

[alwinm]

initializing some member variables in the OneTime class.

This looks great to me! I think all those things were left uninitialized because they get set/overwritten later anyway.