[WIP]nexus rmg updates

[kgasperich]

Please review the developer documentation
on the wiki of this project that contains help and requirements.

Proposed changes

• add RMG to ppset known codes
• drive RMG NSCF workflow with Nexus
• drive SD-DMC calculation workflow with Nexus starting with RMG orbitals

What type(s) of changes does this code introduce?

Delete the items that do not apply

• New feature

Does this introduce a breaking change?

• No

What systems has this change been tested on?

• Laptop

Checklist

Update the following with a yes where the items apply. If you're unsure about any of them, don't hesitate to ask. This is
simply a reminder of what we are going to look for before merging your code.

• Yes. This PR is up to date with current the current state of 'develop'
• No. Code added or changed in the PR has been clang-formatted
• Yes. This PR adds tests to cover any new code
• Yes. Documentation has been added (if appropriate) : Full nexus example.

[jtkrogel]

@anbenali what is still needed to move this out of WIP for review?

[anbenali]

I want to have it working with the MSD route as well. However, we can still just create another PR.

[prckent]

Better to keep things moving imo.

[prckent]

Checking on the status of this. It still has [WIP] but does anything still need to be done besides solving the conflict on qmcpack.py?

[jtkrogel]

@anbenali @kgasperich ping

[prckent]

Ping. Can you remove the wip or is another update needed?