User-friendly error messages

[aramalipoor]

In some situations the error shown to the user is not very explanatory.

Some that I've faced are as follows:

• When a box name already exists: Error 1062: Duplicate entry 'myapp' for key 'name'.
  Can be: Box with name 'myapp' already exists.
• When a box with provided name does not exists: Unexpected response from Farmer server. (record not found).
  Can be: Cannot find box 'myapp'.
• When deploying fails because of status script exit: Exited with code 1
  Can be: Failed to deploy revision Automatic ubuntu/trusty64 box url #2 on box myapp. Exit code is 1.

[majidgolshadi]

Farmer doesn't have statistic and log system yet.
I think we will cheange these messages to firendly ones when we add log feature in v0.4 mileston.
This need add more layers to handle error in Farmer.

[aramalipoor]

👍