Add tab completion
Adding a concourse-testing project
Better server side prefs handling

Define defaults prior to instantiating ConcourseConfiguration object
so we can gracefully use defaults if prefs file isn't available
Add repro for CON-4
CON-4: Make sure the Describe method always returns the correct results

This commit fixes and issue where the describe method would drop a key if it appeared once
in the buffer and once in the database.
1. Use union instead of xor for results returned from buffer and database
2. Determine the result of the buffer by examining the type of the Write instead of the
number of times equal writes have appeared
Enable buffer dumping