feat(src): replace DisplayView with hide, show on clock parts

The clock is meant to show only clock, so introducing
DisplayView trait was an overkill, a simpler
solution has been implemented instead.

Previous solution did not allow for showing and hiding individual parts,
hiding parts may be useful when setting time, to blink the current part
being set.

feat(src): add setter methods for Calendar

Allows to change the current date of
already existing calendar.

tests(src): add tests for calendar tick functions

feat(src): implement Calendar::from_ticks for arbitrary year, add Calendar::to_ticks

So far, Calendar::from_ticks could not correctly parse
other month than the base month, this commit fixes that.

Calendar::to_ticks may convert any Calendar date to seconds passed from
the base year. The base year is remembered in Calendar instance.

chore(src): format with fmt

feat(src): split main into multiple functions

Merge pull request #1 from Rutherther/add-docs

Add basic documentation

docs: add basic documentation

Adds a readme, with images of the product,
mapping of the pins to peripherals,
the readme contains a roadmap and
description of the hardware used.

fix(src): remove unnecessary import

feat(hw): add KiCAD project, schema and pcb

chore: add MIT LICENSE

feat(tests): add full checkup testing peripherals

Tests all peripherals, observation should point
out to where an error is, if any.

feat(tests): add rtc counter test

chore: move .gitignore to root

chore(src): move source to source/ folder

feat(src): add clock application and initialization

feat(src): add brightness manager

feat(src): add module for linear interpolation

feat(src): add basic button representation

feat(src): add app state with calendar