chore(src): format with cargo-fmt

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.

chore(src): move source to source/ folder

feat(src): add clock seven segment display support