Added feature to calculate BMR and daily calories based on activity level

[a124557]

This patch addresses issue #238.

The following features were added:

1. In Weight Track -> Index, the BMR for the user is calculated based on two formulas, the Mifflin-St Jeor equation, and the Katch-McArdle formula. The latter formula is said to be more accurate for individuals who are leaner. For those with body fat levels equal to or lower than 15%, the app uses the Katch-McArdle Formula to calculate BMR. When body fat is greater than 15%, the Mifflin-St Jeor equation is utilized. The body fat cutoff value can be changed.

2. Estimated daily calories are now provided in Weight Track -> Index as well. This calculation is based off the user's BMR. A spinner allows the user to select their activity level. This selected activity level is saved even when the app is closed. Depending on which activity level is selected, a different multiplier is used against the BMR to produce the daily calorie value. If the user decides to change the activity level, the daily calorie recommendation will be updated in real-time.

The equations used to perform these calculations can be referenced here: https://www.calculator.net/bmr-calculator.html

Screenshots have been provided for more info.

Please let me know if you have any questions/comments.

Thanks

[brodeurlv]

Hi @a124557, thank you for the pull request. That's a good addition to the app which integrates well with the other current option.
However, could you please initiate a discussion with me before doing too much work on your side just in case there is already work in progress on my side on similare topics ? Here that's fine anyway, but next time that would be safer.

Can you confirm that the pull request has been fully tested ? I see several additional commits to fix UI or strings. Thanks.

[a124557]

Hi @brodeurlv,

Sure. I will let you know before implementing any new features or fixes.

Since the last commit, I have not encountered any issues so far with this PR while using the app. The translations are missing for this PR. I'm not sure if using google translate would have been reliable since I couldn't verify the accuracy of the translations.

Regards,

@a124557

[brodeurlv]

Thank you @a124557.
For the translation, I will wait for weblate to propose something.