Profiles may be overwriten without warning

[JiriPavela]

Perun currently does not warn the user when a profile is about to be overwritten, e.g., during back-to-back imports or when a --profile-name parameter is supplied. Perun should instead:

• warn the user when a profile is about to be overwritten, unless some form of force parameter is provided;
• allow the user to supply a new name, fallback to an automatically generated name, or abort the operation.

Moreover, in cases when overwriting a profile is indeed the intended behaviour, the old profile label should be overwritten as well, if supplied. Currently, the old profile label is not overwritten by a new label.