Inform the user about deprecation and upgrade options

[maybeec]

As a cobigen user, I want to get automatically informed about the conceptual changes of the configuration going from monolithic template configuration folder to a modular template-set configuration folder. I want to get offered information (#1516).

Acceptance Criteria

• If cobigen reads my monolithic template configuration, which is deprecated, I want to get offered an upgrade option and get informed about the process and steps to be performed
• To properly make my decision in the moment of time, I would like to get more information about why I should do the upgrade and what is the impact
• the user should be asked every time a monolithic configuration is read from a folder
• make sure, that maven execution is not blocked by this feature at all

[maybeec]

Hey team! Please add your planning poker estimate with ZenHub @EduardKrieger @GuentherJulian @jan-vcapgemini @LarsReinken @mdukhan