Project detection: drop site folder requirement

[swalkinshaw]

This makes the project detector more flexible and less strict by dropping the site folder requirement. Previously the detector would only recognize the recommended folder structure when not directly inside a trellis folder. Your project would have to be structured like this:

example.com/       # → Root folder for the project
├── trellis/       # → Your server configuration (a customized install of Trellis)
    └── .trellis/  # → trellis-cli config directory
└── site/          # → A Bedrock-based WordPress site
    └── web/

site was required to limit false positives but isn't necessary due to the other requirement for the .trellis config directory.

By dropping the site requirement, this means trellis-cli will work better in two other known folder structures:

• where the "site" folder exists but it named differently some_project_name/ # → Root folder for the project

├── trellis/       # → Your server configuration (a customized install of Trellis)
    └── .trellis/  # → trellis-cli config directory
└── example.com/   # → A Bedrock-based WordPress site
    └── web/

• where the root is the site contents, and trellis is a subdirectory

example.com/       # → A Bedrock-based WordPress site
└── web/
├── trellis/       # → Your server configuration (a customized install of Trellis)
    └── .trellis/  # → trellis-cli config directory