doc/definitions.rst * deleted NLTK-API, NLTK-BOOK as the URLs are now too long to be useful;   everything can just use NLTK-URL.
doc/definitions.rst
* deleted NLTK-API, NLTK-BOOK as the URLs are now too long to be useful;
  everything can just use NLTK-URL.

doc/en/*.rst
* changed URLs to use NLTK-URL instead of NLTK-BOOK, etc

nltk/downloader.py
* fixed typos that prevented download_gui() from working

nltk_data/index.xsl
* added more prose to the top of the page so that users know
  they don't have to download the data using this page


svn/trunk@7051

nltk/nltk,nltk/nltk,nltk/nltk