[wip] Update pixel and object classification for 1.3.2

[k-dominik]

fixes #28
Summary:

• Pixel Classification:
  • use specifiable sigmas + 2d/3d documented
  • updated screenshots
• Object Classification
  • updated screenshots
  • document object features fixes object classification: vague description of neighborhood features #4, fixes object classification: missing explanation of halo size #5
  • document table export

[k-dominik]

closing this in favor of #73 and #72