loader: Skip loading theme CSS with a custom css code

loader: Skip loading theme CSS with a custom css code

  If applications have <link rel="stylesheet" href="[theme CSS path]">,
loader skips putting new <link> tag for the theme.
  This option only works with proper theme CSS path: if the <script> tag
loads "<path>/<version>/js/tizen-web-ui-fw.js", then the theme CSS path must
be "<path>/<version>/themes/<theme>/tizen-web-ui-fw-theme.css",
having exactly same path to the script path. Otherwise, the link tag will be
ignored, and the new <link> tag will be added automatically.

Change-Id: I9910eb3049f5a73fdc386c40b73409f166dfa1c3