Sonicwall: Improve documentation

[StefanAustin]

Add new categorization
Add a note about message field is shortend -> full_message to see all.

[StefanAustin]

Wait until 6.2 is created. Need to add or change:

Requirements:

Graylog version 6.0.1 -> remove single field function

Log Message Processing

Note: To reduce license utilization, the message field is overwritten by the vendor_message field. If the full message is needed, activate the Store full_message feature in the input.

14 120000 network, network.network connection, network connection
36 120000 network, network.network connection, network connection
97 120000 network, network.network connection, network connection
263 102500 authentication, authentication.logoff, logoff
355 120000 network, network.network connection, network connection
356 120000 network, network.network connection, network connection
524 120000 network, network.network connection, network connection
526 120000 network, network.network connection, network connection
1226 129999 changed, network, network.default, network message
1573 129999 network, network.default, network message