Better warning messages

[rdbende]

I don't want to write a complete novel for every check, but a little explanation would be helpful for those who don't understand why their code is bad.

Also the current messages are really inconsistent in wording.

[meprajwal]

Go throughly. It's clean enough to understand.

[rdbende]

@Moosems?

[Moosems]

Pretty self-explanatory to be honest if you know what you're doing.