* Properly override WebSite Document in erp5_web_shadir by creating a new
  version_priority.
* Keep Web{Section,Site}TraversalHook in Product/ERP5/Document as these are
  not ERP5 objects. Also, add `kept_for_backward_compatibility_only` to
  importLocalDocument() to handle pattern where the Document class has been
  migrated but some code remains.
* Move WebSection_get*PrecacheManifestList Python Script from bt5 not depending
  on erp5_web to erp5_web_renderjs as this is required by CodingStyleTest
  (WebSection being now in erp5_web).

There are 2 shemes for VIRTUAL_URL_PARTS:
- 2-tuple with SERVER_URL and subpath
- 3-tuple with SERVER_URL, vh path and subpath
This code only supported the 2-tuple version, add support for the 3-tuple
version.

Like Document and Interface Components for the same reasons (694c9fee).

url
- corresponding test added

Defining it inside portal_components ledds to business template update issue.
Bypass it by defining the expected behaviour into the web section hook.

WebSite redirection must be tested against different virtual host monster configuration
TODO: No idea how to fetch the ipv6 in live test

erp5_web: Fix Display Static Web Section in Web Section and Web Site views