[Feature] Edit configuration via command line

[saroad2]

Description
One should be able to edit configuration using only the command line.

Tasks:

• General
  • Set mode
  • Set history size
  • Show config file content
  • Initialize config
  • Remove config
• Contexts
  • Add context
  • Remove context
  • Edit context
  • Add alias
  • Remove alias
  • Set parent
  • Clear parent
  • Rename
  • Remove all contexts
• Commands
  • Add command
  • Remove command
  • Edit command
  • Add context specification
  • Fix versions
  • Remove all commands
• Sources
  • Add source
  • Remove source
  • Edit source
  • Show commands tree
  • Remove all sources