Make the generated URLs shorter

[oanalavinia]

Right now the generated URLs are of the following form http://localhost:8080/xwiki/rest/p/{pageID}. The idea of this issue is to remove the rest part, making the URLs as http://localhost:8080/xwiki/p/{pageID}.

Then all new links (links copied using the Get shortened URL button) will be of this form.
Note that any link copied previously to this implementation will continue to work as expected, to not break backwards compatibility.

This needs to be done by using https://extensions.xwiki.org/xwiki/bin/view/Extension/Resource%20API#HAddinganewResourceTypeHandler

[vmassol]

Note that it's not just about making it shorter, it's also about making it more logical. Using a REST action for something that doesn't produce REST is weird and incorrect (REST is for machines and a REST endpoint is not supposed to produce rendered HTML for humans).

[vmassol]

BTW what does p stand for? :)

[oanalavinia]

p stands for page :)