connecting.md: improve and re-organize console help description

Summary

• connecting.md: improve and re-organize console help description
• connecting.md: describe feeding picodata admin with a file

• Close #307 (closed)
• Depends on !1179
• Cherry-pick to: none
• Staging: https://docs.binary.picodata.io/picodata/at_console_keys/tutorial/connecting/