Add the Create a new post to category pages - when used by default select that category

As dicussed on the mailing list I created this request on request of Sergiu Dumitriu.

Currently the 'Create a new post'-action can only be done from the Blog main page.
It would be nice if this functionality can be added to subcategories.
An extra nice feature would be that if the post is created, it automatically sets the checkbox for that category.

Adding the post should be simple by reusing the code, I do not know about the category.

Practical example:
We use the blog as a logging system for servers, applications, etc.
We have categories for example for Servers , with subcategory Linux, Solaris and Windows.
We use these blogs as kind of a log for events happening to that category.
So when we are in category Linux, we would like to be able to click on 'Create a new post' which shows a new screen with the category Linux checked.

This might or might not be combined with this:
http://jira.xwiki.org/jira/browse/XSCOLIBRI-104
It should not be in Colibri only I suppose.

One could consider if either or both would be nice to have.
I do not see why the couldn't be implemented both , maybe a voting would be appropriate?