FLUME-410 Add ability to tail subdirs to tailDir sink

Review Request #1313 - Created Dec. 17, 2010 and submitted - Latest diff uploaded

Alex Baranau
Add additional parameter to tailDir source to make it recurse into subdirectories for watching/tailing files. Ideally add parameter which defines max depth of recursing.
test performed for tailDir with param recurseDepth=2, in test:
* checked tailing existing subdirs
* adding subdirs checked
* checked max recurseDepth