Fix demo themes (home-assistant#5643)

Merge pull request home-assistant#5641 from home-assistant/dev

Merge pull request home-assistant#5620 from home-assistant/dev

Merge pull request home-assistant#5586 from home-assistant/dev

20200422.0

Bumped version to 20200418.0

Merge pull request home-assistant#5539 from home-assistant/dev

20200414.0

Fix first logbook item not being shown (home-assistant#5491)

Merge pull request home-assistant#5487 from home-assistant/dev

20200407.1

Merge pull request home-assistant#5481 from home-assistant/dev

20200407.0

Merge pull request home-assistant#5471 from home-assistant/dev

20200406.0