Review Board 1.7.22

FLUME-1181. Context must enforce dot-separated prefix for subproperties

Review Request #5017 - Created May 5, 2012 and submitted

Arvind Prabhakar
brocknoland, hshreedharan
This change:
* introduces a precondition check in Context.getSubProperties(String prefix) method enforce that the prefix ends with a period,
* fixes the TestPropertiesFileConfigurationProvider to load the property file which was previously not working, and fixes cases that are broken
* refactors some of the source (not all) to externalize the configuration keys into separate constants class
Ran all tests. The updated TestPropertiesFileConfigurationProvider catches two issues now - the one with channel selector configuration not being set correctly, and the other a similar issue with syslog source format configuration. Both of these issues have been fixed with the changes.

Also done some manual validation of the system with a few simple scenarios.
Review request changed
Updated (May 5, 2012, 8:18 p.m.)
Thanks Hari and Brock for the review and feedback. This diff incorporates the feedback and rebases the patch on the latest trunk.