Integrated OpenAddressMapper with the main app.

Added OpenAddressMapper to the main application by adding a JSON string
selector to enable creating this type of Mapper. Also changed the settings
structure to read in settings for HwNmu settings such as growth and shrink
thresholds and index list load.

Bug fix: I found and eliminated a major bug that invalidates all old
simulations. The scaleUpMap() and scaleDownMap() functions in HwNmu
were using u64 division for determining load and as such anything less
than 1.0 was rounded to 0.0. I changed this to use f64 division and it is
now working as expected.