Extension naming: Rename back to "SlicerWMA"

[jcfr]

Instead of renaming the extension, I suggest to update the README describing the current maintenance state.

Then, you may also consider:

• archiving the corresponding SlicerWMA extension
• archiving this repository. For an example of archival, see https://github.com/SCIInstitute/Cleaver1

cc: @ljod @pieper @lassoan

[jcfr]

cc: @pieper @ljod @jamesobutler @jhlegarreta

[pieper]

@zhangfanmark