Replace String Comparisons with Direct Field Comparisons

[daniel-stoneuk]

Difficult to describe this issue clearly. Currently the library generates strings for the items so that DiffUtils can compare and only update items that have visually changed. I got into this habit since I think it's what the DiffUtil documentation uses! As @Robyer mentions in issue #77, this isn't a great way of checking - it would be much more efficient to create equals-like functions.

This optimisation can be applied to both the preferences and the main branch.