Update model to only work in metric

All linked to Issue #9
Remove references to the unit setting
Updated record view to pass kgs

Specifically fixing Issue #9
Improve conversion variable naming conventions
Update record view to only use metric (cm)
Add additional comments to model methods
Update model comments and variable naming conventions
Update record ViewModel calculations naming conventions
Merge pull request #14 from bergenhem/api-updates

Resolve Issue #9 and Issue #10