[Nutch Wiki] Update of "HttpAuthenticationSchemes" by susam

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The following page has been changed by susam:
http://wiki.apache.org/nutch/HttpAuthenticationSchemes

The comment on the change is:
Added TableOfContents and minor edits in Prerequisites and Optional sect

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+ [[TableOfContents]]
+ 
  == Introduction ==
  This is a feature in Nutch that allows the crawler to authenticate itself to websites requiring NTLM, Basic or Digest authentication. This feature can not do POST based authentication that depends on cookies. More information on this can be found at: HttpPostAuthentication
  
@@ -18, +20 @@

  Since the example and explanation provided as comments in 'conf/httpclient-auth.xml' is very brief, therefore this section would explain it in a little more detail. In all the examples below, the root element <auth-configuration> has been omitted for the sake of clarity.
  
  === Prerequisites ===
- In order use HTTP Authentication your Nutch install must be configured to use 'protocol-httpclient' instead of the default 'protocol-http'. To make this change copy the 'plugin.includes' property from 'conf/nutch-default.xml' and paste it into 'conf/nutch-site.xml'. Within that property replace 'protocol-http' with 'protocol-httpclient'. If you have made no other changes it will look as follows:
+ In order to use HTTP Authentication, the Nutch crawler must be configured to use 'protocol-httpclient' instead of the default 'protocol-http'. To do this copy 'plugin.includes' property from 'conf/nutch-default.xml' into 'conf/nutch-site.xml'. Replace 'protocol-http' with 'protocol-httpclient' in the value of the property. If you have made no other changes it should look as follows:
  {{{
  <property>
    <name>plugin.includes</name>
@@ -35, +37 @@

  }}}
  
  === Optional ===
- By default Nutch use credential from 'httpclient-auth.xml'. If you wish to use a different file you will need to copy the 'http.auth.file' property from 'conf/nutch-default.xml' and paste it into 'conf/nutch-site.xml' and then modify the '<value>' element. The default property appears as follows:
+ By default Nutch uses credentials from 'conf/httpclient-auth.xml'. If you wish to use a different file, the file should be placed in the 'conf' directory and 'http.auth.file' property should be copied from 'conf/nutch-default.xml' into 'conf/nutch-site.xml' and then the file name in the '<value>' element should be edited accordingly. The default property appears as follows:
  {{{
  <property>
    <name>http.auth.file</name>
@@ -43, +45 @@

    <description>Authentication configuration file for 'protocol-httpclient' plugin.</description>
  </property>
  }}}
- 
  
  === Crawling an Intranet with Default Authentication Scope ===
  Let's say all pages of an intranet are protected by basic, digest or ntlm authentication and there is only one set of credentials to be used for all web pages in the intranet, then a configuration as described below is enough. This is also the simplest possible configuration possible for authentication schemes.