INT-3099 Add IMAP Idle Application Events

Allow an application to be informed of problems on the IMAP idle
thread by emitting an event containing the exception.

Introduce IntegrationApplicationEvent hierarchy for all
events emitted by SI components.

INT-3099 Polishing (PR Comments)

Separate TCP events into discrete subclasses.
INT-3090 Document File IGNORE and Temporary File

IGNORE applies to the temporary and final file names.