Be able to have several set of ideas in a given wiki

Right now, it seems the app only supports one set of ideas in a wiki... That's really limitating.

For example I may want to have one page for defining ideas for the Roadmap of a product and another page for defining ideas for How to improve the release process, or for ideas about how to improve the office's life. All in the same wiki.

Implementation idea:

• Be able to define where the ideas are stored and allow to store them a nested pages of a given page.
• Then use the {{ideasrecent}} macro to list all ideas from nested pages of the current location and/or add a macro param to specify the root of idea pages.
• Modify the macro so that the "create idea" button creates an idea in the defined storage location.
• Add an xproperty to the idea xclass to represent the topic (ie set of ideas) + make this a mandatory parameter of the ideasrecent macro
• Modify the idea home page to provide a LT displaying all idea topics in the current wiki. When you click on a topic you get to see a LT listing all ideas for that topic.