Additional ServiceCollection extension methods

[andrewmckaskill]

These overloads allow for backwards compatibility between v3 and v4 when used inside Umbraco - allowing a v4 package to be substituted without re-compiling the entirety of Umbraco.

Reason:
Even though the new FacetsConfig parameter is optional and has a default value provided, existing packages that are built against v3 fail to bind to this method, producing a System.MissingMethodException:

System.MissingMethodException: Method not found: 'Microsoft.Extensions.DependencyInjection.IServiceCollection Examine.ServicesCollectionExtensions.AddExamineLuceneIndex(Microsoft.Extensions.DependencyInjection.IServiceCollection, System.String, Examine.FieldDefinitionCollection, Lucene.Net.Analysis.Analyzer, Examine.IValueSetValidator, System.Collections.Generic.IReadOnlyDictionary`2<System.String,Examine.Lucene.IFieldValueTypeFactory>)'.
   at Umbraco.Cms.Infrastructure.Examine.DependencyInjection.UmbracoBuilderExtensions.AddExamineIndexes(IUmbracoBuilder umbracoBuilder)

By changing the new parameter to be made available as a traditional overload instead of an optional parameter, the original method signature is kept the same and is found via reflection.

[Shazwazza]

Looks good, but I'm not sure what will happen if we are passing in a null facets config. @nikcio any ideas?

There's still a bunch of work for v4 to go, just needs time for testing/review.

[nikcio]

@Shazwazza if the facetsconfig is null it will instanceiate the default facetsconfig so I'll should be fine. (This happens on line 115 in this file) 😉

[nikcio]

@Shazwazza once we get #313 merged it should also be easy to see if we are passing null where we shouldn't (in new code from PRs) as it will create a warning. 😄

[nikcio]

@andrewmckaskill Same here: #340 (comment)

[nzdev]

#347 ensures api compatibility for all of the v3 public api

[andrewmckaskill]

Closing in favour of #347