Optimize the algorithm generating the map (~35x speedup), remove some features and legacy code.

[mikispag]

This PR:

• greatly optimizes the algorithm generating the map (based on #33)
  • On the same hardware, with a scale factor of 2, it can compute the map in ~400ms versus ~14000ms (~35x speedup).
• avoids unnecessary computations, caching full maps and map layers
• supports map compression
• supports base-64 encoded maps
• removes support for old binary maps, supporting Valetudo 2021.01.1+ only
• removes the webserver
• removes support for overlay/underlay images
• removes support for manual cropping.

[llnnse]

Is it possible to bring back the webserver? As it broke my automation for displaying the map in homebridge.