Improve package structure, refactor Manage Symptoms Screen

[carstenhag]

This refactoring includes many bugfixes relating to the Manage Symptoms screen:

• When symptoms were getting create + colors were changed, the color values were not saved to the correct symptoms. It was just overall buggy.
• Symptom creation now requires the user to type in a symptom name. A blank name is not valid anymore

Important changes:

• Package structure of the app was changed
• PeriodDataBaseHelper no longer calls db.close. At ManageSymptomsViewModel I introduced withContext(Dispatchers.IO) {, which performs the DB calls in the background. Multiple DB calls at the same time are fine. But not, when one has completed and calls db.close() while the other is still interacting with the DB.

Minor fix: Display cutout insets at Settings screen, insets fixes at MensinatorApp