add ExtractLinks and PrefixQuery(ExtractSiteLinks)
update README file, add steps for getting URLs and extracting links
trival update Readme file, modify format
add Lucene FST prefix search
add prefix search feature to UriMapping class; add test class for UriMapping PrefixSearch
remove TestFSTPrefix class
Merge branch 'extract-links' of github.com:Jeffyrao/warcbase into fst

Conflicts:
	src/main/java/org/warcbase/data/UriMapping.java
Light refactoring, fixed a few errors.
Exposed -getPrefix command-line option.
Updated documentation.
Fixed Issues #16, #19, #23