Changed interface between traversal & mediator/union to pass a callback
function instead of a set of filenames to ignore. The function implemented
for Aufs replicates the previous ignore_files functionality, but the new
interface can examine more than just the filename (useful for union/overlay
filesystems that denote special files in other ways such as by using xattrs)
Changed name of IgnoreFileP() to IgnoreFilePredicate() for clarity.

Fixed some inadvertent tab-to-spaces whitespace issues.
Merge branch 'master' of https://github.com/cvmfs/cvmfs into cvmfs-master

Conflicts:
	cvmfs/sync_mediator.cc
	cvmfs/sync_mediator.h
add a generalized form of the catalog counter classes
TEST: unit test for new catalog counter classes
add missing file header
encapsulate data types for Counters and DeltaCounters
add a mapping from SQL key names to counter fields
move external library configuration into root CMakeLists.txt
The libraries are needed in both the ./cvmfs and the ./test/unittests subdirectories
integrate database read/write with catalog::Counters
replace catalog statistics counters in the codebase
FIX: WriteToDatabase always failed
remove (preliminary) chunked file counters
add an SQL wrapper for creation of new catalog counters
fix watchdog with micro syslog
integrate chunked file statistics counters
integrate chunked file statistics into test case
add a sql command to count the chunks of a specific file
count file chunks when updating catalogs
check chunked file counters in swissknife_check