Review public API surface

[bart-degreed]

Things I'd like to change:

• Rename 'entity' parameters to 'resource' in DefaultResourceService
• Rename DefaultResourceRepository to EntityFrameworkCoreRepository (and update variable/parameter names likewise)
• Move all types required for basic usage into JADNC's non-internal namespace. Advanced usage, like custom Service/Repository/ResourceDefinition and query filters can be in Internal namespaces. This should clarify our intent on taking breaking changes.
• Make options.DefaultPageSize nullable (disallow setting to 0)
• Rename T in JsonApiController<T> to TResource
• Rename IQueryParameterParser to IQueryStringParser (it parses all types, not a single one)
• Replace IEnumerable<> / List<> with IReadOnlyCollection<>
• Review null checks
• Validate input parameters on public members, validate options.
• Rename CurrentRequest to JsonApiRequest

Other

• Remove the various .gitignore files that are spread around in the repo, and update the root version from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore - Replaced duplicate .gitignore files and updated root version #743
• Cleanup launchsettings.json, enable https - Projects cleanup #744
• Cleanup excessive logging in AppVeyor - Projects cleanup #744

[maurei]

Rename DefaultResourceRepository to DefaultEntityRepository (and update
variable/parameter names likewise)

What would be the motivation for this?

[bart-degreed]

It is an implementation of a resource repository that uses ORM entities. Other implementations could be named AmazonResourceService, CachingRedisRepository etc.