Re: [PATCH] HttpRequest::helperNotes to NotePairs

This patch try to fix current current Notes interface and usage.

The changes done having in mind that we need:
1) to add multiple notes with the same key
2) to support 3 different note types: adaptation meta headers, helper
notes and custom notes added by the system administrator
3) to log notes using the %note formatting code
4) to use the %note formating code everywhere the formating API is used.
For example use the %note with the request_header_add configuration
parameter.
5) to use notes with ACLs.

The NotePairs class is implemented from scratch. It stores the notes in
a simple key:value pairs list, which just allow multiple entries with
the same key. I have an implementation which uses a
"key:value1,value2,value3..." form but my sense is that the
implementation I am posting here is simpler and faster.

- The %{key}notes prints a coma separated list of note values which have
the key as key. Eg the %{user}note will print:
 "J, Smith",chtsanti

- The %notes prints a "\r\n" separated list of key:value pairs:
  user: "J, Smith"\r\nuser: chtsanti\r\n

- The %notes formating code can be used now with request_header_add and
other similar configuration parameters.

- The Helper response may needs fixing. For example if the helper return:
      user="J, Smith",chtsanti
  The user:"J, Smith,chtsanti" note will be stored. This is because of
the strwordtok function used to parse responses.

 - We may need to merge the AccessLogEntry::notes and
AccessLogEntry::helperNotes/HttpRequest::helperNotes to the same object.
The adaptation meta headers maybe can be merged to the same object to.

Some details also exist in the patch

Regards,
    Christos