Further simplify addressing & linear index

This removes some more unnecessary abstractions from the addressing module.
It also removes some dead code from LinearIndex (because all addresses are now
numeric) and it removes temporary arrays created in LinearIndex (we can just
address keys directly).
Merge changes
Add pivot table docs, minor stylistic code changes

The pivot table function is cool :-) I added a few samples to the docs.
I also did a few minor changes (as I was reading the code) - there
was absolutely nothing wrong with it - I did just a few minor stylistic
tweaks and adjusted it to a small notebook screen!
Fix build error and unit tests
Fix of by one errors - tests now pass
Merge pull request #130 from tpetricek/mainline

A few additions to the mainline version