Code quality / refactor

[KonradIT]

• cmd:
  • Rethink how to use customCameraOpts
  • importFromCamera should be an interface with each camera's Import being used
• pkg
  • Privatize more const/vars
  • more error.Is / check for specific errors
  • Catch OS errors and wrap them with custom
  • Network: custom timeout from config
  • Standardize network functions as much as possible
  • Do network test before anything
  • Check if file exists before creating it in all cases
  • Additional logging, disabled by default, to file
  • Use experimental go 1.18 stuff, like golang.org/x/exp/slices and replace for loops, while searches, etc...
  • Go over nolint statements
  • add more linters
  • avoid code repetition
  • Named loops