sample client for Storage packages

[ChuikoSergey]

PR contains base implementation for storage client that use Storage packages. Core project:

• Internal Exceptions, Models, Enums
• Interface for file storage service Domain project:
• Implementation for IFileStorageService WebApi project:
• Services registration
• Public API for client
• Storage provider for current request selector

Implemented actions:

• Download file (as FileStream)
• Upload file
• Delete file Actions implemented only for FileSystem storage as an example of implementation. To use another storage developer should add storage registration in 'AddStorageService' and add new controller like 'FileSystemStorageController'.

SampleClient is not a part of the 'Storage' solution and uses NuGet packages, not project dependencies.