Added empty settings page.
Added two empty pages in settings + navigation logic.
First version of settings HRmax and displaying associated HR zones.
Adding basic HTML skeleton for running/cycling pace zone settings.
Added proper form & validation to enter recent running result.
Splitting performance settings into separate files per section.
Added Edit-Save/Cancel flow for HRmax editing.
Form editing logic abstracted away into some generic code.
Settings: editing running performance data (WIP)