patch for changes related to TestNDFS

[Paul Baclace <pe...@baclace.net>]

This patch is for comments/local name change or error
msg change only, to clarify the code as it relates to
the new JUnit test, TestNDFS that I wrote.  In many
cases the intention was to help the next person reading
the source.  These changes should be very safe and
are unlikely to introduce subtle bugs, but they are
not required for TestNDFS.

Affected files:

src/java/org/apache/nutch/crawl/Crawl.java
src/java/org/apache/nutch/fs/NDFSFileSystem.java
src/java/org/apache/nutch/mapred/JobConf.java
src/java/org/apache/nutch/fs/NutchFileSystem.java
src/java/org/apache/nutch/mapred/JobConf.java
src/java/org/apache/nutch/ndfs/NDFSClient.java
src/java/org/apache/nutch/ndfs/DatanodeInfo.java

The biggest change is to DatanodeInfo.java:
   Made fields private, added javadoc comments,
   removed commented-out code, renamed fields for clarity.

The changes to Crawl.java and JobConf.java might be considered nit-picky.

Some inadvertent whitespace changes are also in the patch.