Item7111: Log user agent for all users; log additional info via extralog URL parameter

1. Always show user agent for view script action, regardless if guest user or not
2. Ability to log extra info via URL parameter

Sample TWiki log entry:

| 2012-12-28 - 16:46 | guest | view | Plugins.HeadlinesPlugin | Mozilla | 66.249.74.176 |

Currently, the user agent (Mozilla in this example) is only shown in the log for guest user, not for authenticated users.

Change: Always show user agent if available, regardless if guest user or authenticated user.

Additional enhancement: If URL parameter extralog is present for view script, its value is added to the log next to the user agent.

For example, http://twiki.example.com/do/view/Plugins/HeadlinesPlugin?extralog=hello+world would show this log entry:

| 2012-12-28 - 16:46 | guest | view | Plugins.HeadlinesPlugin | Mozilla hello world | 66.249.74.176 |

This is useful to log extra information, for example to have additional analytics available when custom search crawlers or cache scripts are used.

-- TWiki:Main/PeterThoeny - 2012-12-28

This is now in SVN trunk and 5.1 branch.

I have done this for TWiki:Plugins.TWikiGuestCacheAddOn so that topic caching action is logged in the TWiki logs.

-- TWiki:Main.PeterThoeny - 2012-12-29

Small additional change: User agent is only shown for view script.

-- TWiki:Main.PeterThoeny - 2012-12-29