Make all network requests wait for a response

[DonatJR]

To be able to report success / errors

Idea:

• do this directly in send / receive of network manager
• make message types for success / specific errors
• pair error messages with error strings
• handle these in the caller, e.g. chooser starts cage but it cannot run as programs are already open on normal desktop -> error message gets reported to chooser -> chooser can display message box to inform user

[DonatJR]

for now, I only implemented a simple boolean true / false as the return value of sending messages, in the future this could be expanded to an enum with possible values: success, timeout, failure, ... also, the result message is a simple string for now, this could also be changed to an enum with predefined messages if needed