Version Bundle management methods

Added `AddVersion(Project project, ProjectVersion version)`, `DeleteVersion(Project project, string versionName`, and `GetVersions(Project project)` methods to enable users to create, list, and delete versions from a project's version bundle. New types for project version and version bundle have been created. A unit test has been written which creates a new version, retrieves the list, and disposes of the new version, which works well against my local YouTrack server.