[devguide_log4j] refactor

[duncdrum]

Where is the problem

Supersedes #12 see eXist-db/exist#1662

What is the problem

The article is big on details, but small on basics. Such as:

• default location of log files
• how to change configuration
• a code snippet how to use it internally
• code snippet how to use it from xquery code
• examples how to integrate it with remote services

there are still traces of stylistic gems, which are no longer in line with the new author guidelines.

Please provide the following

• exist-db version: 4.0.0
• documentation version: 4.0.0

[duncdrum]

see #333

[duncdrum]

ok 1-3 are taken care of, however i would still like to get a listing of all the loggers that exist in there. 4-5 need more work.