Release v0.6.0 (#179)

## Summary

Release v0.6.0 by stripping the `-DEV` prerelease suffix. This is a
breaking release collecting the v0.6 cycle: the `NamedDimsArrays` code
is relocated into ITensorBase under a from-scratch
`AbstractITensor{DimName}` type hierarchy, with the unique-name and
operator cleanups on top.

Included PRs:

- Relocate the NamedDimsArrays code into ITensorBase
(#163)
- Rename the named-array types to an AbstractITensor{DimName} hierarchy
(#164)
- Drop the AbstractArray supertype from AbstractITensor
(#169)
- Subtype AbstractNamedUnitRange to AbstractNamedArray, not
AbstractUnitRange (#170)
- Return dimnames as a Vector and the named axes as Tuples, dropping
LittleSet (#171)
- Drop the AbstractNamedInteger `<: Integer` subtyping
(#172)
- Rework named-type parameters around a single `Named` scalar
(#173)
- Make Index an alias for NamedUnitRange{IndexName}
(#174)
- Remove factorize, drop TypeParameterAccessors, rename randname to
uniquename (#175)
- Remove FusedNames and error on ITensor length
(#176)
- Clean up tensor reconstruction and the operator type
(#177)
- Mint unique names from RandomDevice and make the id a UUID
(#178)

Author: mtfishman

Project.toml

@@ -1,6 +1,6 @@
 name = "ITensorBase"
 uuid = "4795dd04-0d67-49bb-8f44-b89c448a1dc7"
-version = "0.6.0-DEV"
+version = "0.6.0"
 authors = ["ITensor developers <support@itensor.org> and contributors"]
 
 [workspace]