Massive code improvements, increased stability, new variants

This is a bigger update. It contains massive improvements in the codebase and should increase the stability very much.

Additionally, there are now three variants of the firmware, that use different modes to drive the LED strips. The old one did use bit banging, which is not recommended and unstable according to the NeoPixelBus wiki. If you want to be on the safe side, use DMA or UART. They are limited in their pin selection and possibly require you to rewire your clock. You can continue to use the bit banging variant, which allows a free selection of pins. It should run reliably, but may crash sometimes. You have been warned.

The clock will now automatically reboot when you change settings that require a restart. And the clock will apply changes to other settings instantly.
The loading and saving of config changes via the web interface should not lead to crashes anymore.
You now can request the Wi-Fi configuration hotspot.
The rainbow and alarm animations now use more fitting color models to render faster and more reliable. It uses a new way to render the alarm and rainbow animation. They are also not as hectic anymore.

There is now a Fritzing sketch to illustrate possible wiring for the variants.