Allow sanitize_text_field() to do its thing without error

The comparison with raw and sanitized data was incorrect and
caused projects with valid names to be rejected.
Use sanitize_title in a better way to allow proper paths

We were rejected too easily with `sanitize_title()` and should allow
a slightly different result from what was typed if spaces were entered
Verify a path is available before creating the site

We use a direct query as `domain_exists()` relies on a network
argument and will not provide a global result.
Merge pull request #3 from washingtonstateuniversity/better-validation

[PR] Provide better validation for name, path, and the existence of path.