As a developer I want to reorganize the project to follow onion structure more closely

Only do this when no other features are currently in development

Acceptance Criteria

[x] - Merge Cheep.Entities and Cheep.DTOs into Cheep.Core project
[x] - Merge Cheep.Infrastructure.Repositories and Cheep.Infrastructure.Service into Cheep.Infrastructure
[x] - Use the AuthorDTO wherever possible
[x] - Only inject Github OAuth if we can get the secret(So check if we have the credentials)
[x] - Wrap all calls to CheepRepository in Cheep.Web to calls to Cheep.Service
[x] - Move scripts to a seperate folder(Instead of just sitting in root)
[x] - Create AuthorRepository and refactor author-related methods from CheepRepository into it