Code cleanup: indentation fixes and remove incorrect TODOs

Also remove some code related to COPY, since the implementation is
not finished, nothing happens as the action is selected.
Code cleanup: Use HttpURLConnection constants instead of magic numbers

Use the HTTP status codes defined in HttpURLConnection instead of
hardcoding magic integer numbers.
Code cleanup: Add constant SeafConnection.HTTP_STATUS_REPO_PASSWORD_REQUIRED
Merge pull request #89 from alfh/fix_code_cleanup

Code cleanup: indentation fixes and remove incorrect TODOs