'Add node form' should add the Custom Path as default value

While using Wikitools, I noticed that this module should add the Custom Path as a default value in the 'Add Page' form. The attached patch should be applied to version Wikitools-6.x-1.1.

I done two simple things, that should be validated by code owners: I created the wikitools_get_page_name() function with wikitools_handle_request() excerpt, that returns the page name and the subpage values, and then used this function in wikitools_form_alter() to include the wikitools Custom Path as a default value.

By adding the Custom Path as a default value, it would improve the Wikitools usability a lot, as the user does not need to include this value by hand for every page added.