[CODAP] Use the CODAP 'hidden' property to manage visibility of attribute columns

[matthew-blackman]

In addressing issues #347 #360 #359 #357, I found that it was much more performant to update the 'hidden' property of CODAP attributes when a variable is checked/unchecked, so that the data table columns are not being rebuilt every time. This also cleans up the wrapper code and preserves the order of the columns, mapping them to the order of the checkboxes. Consulting with @samreid, it looks like this is a solid approach and will also improve our wrapper performance.

Note: This will also fix the 'Save a Copy' issue in #359.

[matthew-blackman]

The above commits addressed several issues. Leaving this open until those issues are resolved.