Enhancement: Unify behavior of verbose

[vikin91]

This PR changes the following:

• Use log package for log messages (this allows to respect -v flag setting)
• Keep using fmt package for commands output (like ls, cat)
• Improved selected error messages: Not a valid -> Invalid
• (automated change) Imports were sorted based on type

Pros:

• This makes errors more visible (they are red),
• This allows to hide unwanted output (by running command without -v)

Cons:

• This shows file and line on output. Example: [INFO] append.go:194 Appended values from ...

What do you think?

[fishi0x01]

I like the idea 👍

I merged your previous PR (whitespaces) to master and updated the branch via GitHub UI. Turns out the whitespace test is failing because the output is missing now. I think adding a -v to the test command should do the trick.

Sorry, I couldn't resist and clicked the Update Branch button - feel free to force-push that away .

[vikin91]

No problem! I also wanted to click it :) Merging master allowed us to spot an issue with the test. I hope bccbc65 would do the job.