Nexus: Add h-channel to list of possible local channels in pseudopotential.

[mcbennet]

Proposed changes

When writing pseudopotential to QMCPACK form, there is an issue if the local channel is h -- namely, the l-value of the local channel (l_local) is set to -1 in this case. This PR resolves this.

Note: The channels are now coded up to 'i'. Furthermore, I think the CASINO code also has the same issue. If so, I can fix this as well along with this PR.

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

• Bugfix

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'
• N/A. Code added or changed in the PR has been clang-formatted
• Yes. This PR adds tests to cover any new code, or to catch a bug that is being fixed
• N/A. Documentation has been added (if appropriate)

[qmc-robot]

Can one of the admins verify this patch?

[prckent]

OK to test