Add 'node-semver' version range comparison functions

[McSherry]

Under node-semver, it's possible to compare a version range against a semantic version to determine more than just whether the version range is satisfied. Similarly, version ranges can be compared and operated on with each other. Supporting this in McSherry.SemanticVersioning seems beneficial as it maintains parity with node-semver on version ranges.

The functions are:

• [ ] outside / gtr / ltr — comparisons to determine whether a semantic version is outwith the range covered by the version range

• [ ] intersects — determines whether two version ranges overlap

• [ ] subset — determines whether one version range entirely includes another

Something to review in doing this will be changes to the node-semver version range specification. At present, we claim compatibility with v6.0.0, but node-semver is now on v7.3.2. Revising our claim to a later version is just good housekeeping.

[McSherry]

Until the situation 5a48a1ce018e45f342b83bae89277d0766317c82 mentions is resolved, this feature is on hold (and so won't be included in the v1.4.0 release unless things change soon).