Fix default tours (several of them don't work, mostly due to changes to Open Atrium)

Several of the default tours don't work. The two main reasons are:

1. Space/Section types now have their own creation pages, and the redirect from (for example) node/add/oa-space to node/add/oa-space/1 is breaking the tour! My PR works around this by rewriting both node/add/oa-space and node/add/oa-section to the first available typed path. You can reproduce this and test the fix by trying the "Banners" tour: it's first step should show a tour popup.
2. There were some NIDs hard-coded in a couple tours. For example, "Colorizing a Space" hard-coded an NID of 4 in the 2nd (and later) steps. My PR works around this by adding another special path (in addition to "firstnode") called "mynode" which returns the most recently created node of a type, which is owned by the current user, and allows you to go to a path based on the node (so, not just directly viewing the node, but redirecting to node/X/group, for example). Look at the diff for a couple examples of what this looks like.

I've been able to click "Next" all the way to the end on all the default tours using this PR! Please let me know what you think.