Prior to this commit, `HasMenuCurrent` and `IsMenuCurrent` on `Node` always returned false.
This made it hard (if possible at all) to mark the currently selected menu item/group for non-Page content (home page, category pages etc.), i.e. for menus defined in the site configuration.
This commit provides an implementation of these two methods.
Notable design choices:
* These menu items have a loose coupling to the the resources they navigate to; the `Url` is the best common identificator. To facilitate a consistent matching, and to get it in line with the menu items connected to `Page`, relative Urls (Urls starting with '/') for menu items in the site configuration are converted to permaLinks using the same rules used for others’.
* `IsMenuCurrent` only looks at the children of the current node; this is in line with the implementation on `Page`.
* Due to this loose coupling, `IsMenuCurrent` have to search downards in the tree to make sure that the node is inside the current menu. This could have been made simpler if it could answer `yes` to any match of any menu item matching the current resource.
This commit also adds a set of unit tests for the menu system.
Fixes#367
The render code path would use a fallback if there was an exception.
This change instead relies on explicit declaration of the layout to use
and includes a check to see if the layout indeed exists before
attempting to render it.
It started with wanting to move templates in template bundles and the
rest followed. I did my best to start grouping related functions
together, but there are some that I missed. There is also the method
Urlize that seems to be a special function used in both worlds. I'll
need to revisit this method.
