Implement oa_clone for cloning nodes (Part 1) and add intermediate Space/Section type page when creating Spaces or Sections.

This is Part 1 of the changes necessary to implement full cloning and 'Space types with content' support in Open Atrium.

*Note: this isn't finished, but it's the most of the major changes that will be made to the way core Spaces and Sections work in Open Atrium! Namely, it adds the intermediate type page when creating them.*

I'll continue to work on finishing the cloning functionality and submit at Part 2 pull request later. However, I think it's important that this gets review early (since it will be the most controversial bit) and that it gets committed upstream sooner rather than later (so there is less conflict with new things that others add in the meantime).

**Here are some of the things it does:**

1. If you click "Create Space" or "Create Section" and there is only one type, it will forward you immediately to the creation page for the only type (btw, it also removes the "Space members" default type, so until users add a Space type, it'll forward)
2. If there is more than one type, it'll show you an intermediate page with the types and descriptions. Here's a screenshot:
    ![selection_097](https://f.cloud.github.com/assets/191561/2103055/cceec7f6-8f66-11e3-90b2-847939130b3e.png)

    **Note:**
    - This is just a view of the Taxonomy terms, so we can add an example image or anything we want here
    - At the top there is a link for users who have permission to manage/add types
    - This page will pass any GET arguments (like ?oa_parent_space=X) to the specific pages, so sub-Space and Section creation still work fine
3. When creating a new 'Space type', you have an option to create them just like previously. See this screenshot:
    ![selection_095](https://f.cloud.github.com/assets/191561/2103082/57ea34ee-8f67-11e3-9f16-8f1955bad0ba.png)
4. But if you switch the type to "Clone an existing Space", you can chose a Space to clone instead: 
![selection_096](https://f.cloud.github.com/assets/191561/2103091/710f09ae-8f67-11e3-96c0-78d20cfd7a1c.png)
5. Here is what the Space creation form looks like if you clicked the "Awesome" type when on the type page: 
![selection_098](https://f.cloud.github.com/assets/191561/2103105/955d83c6-8f67-11e3-9cbd-aeab4b4f7d42.png)
6. You can also find a "Clone this ___" option under the gear on any Space (or other node for that matter): 
![selection_099](https://f.cloud.github.com/assets/191561/2103112/b2035e38-8f67-11e3-8917-3d2f906bac70.png)
7. Clicking this will get you essentially the same creation form, but with the titles a little different for cloning (rather than "Create new ..."): 
![selection_100](https://f.cloud.github.com/assets/191561/2103122/cbc1f2f8-8f67-11e3-99ee-2791c9f1ac32.png)

**Here are some things NOT in this PR:**

- Per-Space permissions for cloning - although, I did look into this and it'll be super easy via hook_clone_access(). This will come in the follow-up.
- Most of the special Open Atrium support for cloning different types, ie. Banner settings, etc. The hooks are all there and I've tested them, but I haven't properly gotten to this yet. This will make up the majority of the stuff in the follow-up!
- Jump links to create a specific Space or Section type without going through the intermediate page. This shouldn't be hard to do and will be included in the follow-up. I would like a little guidance on how these should "look", though - I don't want to clutter the drop-downs in a way that makes them harder to understand.
- Ability to click "Make this space into a Space Type" when viewing a Space. I think this will be a killer feature! Should be pretty easy to implement - but killer. :-)

**Other random notes:**

- Open Atrium will install fine after merging this pull request! But I did find another install issue caused by the oa_buttons refactor, that I've been banging my head against all day. It won't correctly set the "Node types" for any of the default Section types. So, this will affect testing of this pull request on a fresh install, but it isn't this PR's fault. :-) You just have to edit the 'Section types' and add some node types. I'm still working on a fix to the install issue.
- I have some pent up changes to oa_contextual tabs and oa_subspaces that improve the experience with this PR, but aren't strict dependencies. I'll send pull requests for those a little later today.

Anyway, please review when you have a chance! I'll continue working on the clone stuff (ie. I'm not blocked on this) but I'd really like to start working out any pontential issues with this base functionality as early as possible because it changes Atrium in some pretty fundamental ways and I could imagine us going back and forth on it for a while. :-)