These changes were used to test the axis innermost property fix, and
should not have been committed.

It doesn't make sense to calculate the innermost property only when no
tickLength has been provided; the two have little to do with each other.

This allows a page to have multiple placeholders, since we're no longer
tied to unique IDs.

To improve organization with the increasing number of examples, every
example page is now the index of its own subdirectory, which contains
all the files specific to that example.