Add error handling to network requests

[davenewham]

Is your feature request related to a problem? Please describe. When connecting to a server, the error message is quite generic. This makes it hard(er) for the user to identify the issue themselves

Describe the solution you'd like Error handling for when the host is unreachable and error handling of generic subsonic compatible API errors

Describe alternatives you've considered None

Additional context

The following error codes are defined:

Code	Description
0	A generic error.
10	Required parameter is missing.
20	Incompatible Subsonic REST protocol version. Client must upgrade.
30	Incompatible Subsonic REST protocol version. Server must upgrade.
40	Wrong username or password.
41	Token authentication not supported for LDAP users.
50	User is not authorized for the given operation.
60	The trial period for the Subsonic server is over. Please upgrade to Subsonic Premium. Visit subsonic.org for details.
70	The requested data was not found.

source: http://www.subsonic.org/pages/api.jsp