* benchmark: Changed --databases to take a parameter specifiying the size
of the database to benchmark.
* benchmark --databases: Display size of the populated database.
* benchmark --databases: Improve the "addAssociatedFile to (new)"
benchmark to really add new values, not overwriting old values.
Rescued from commit 11d6e2e260 which removed
db benchmarks in favor of benchmarking arbitrary git-annex commands. Which
is nice and general, but microbenchmarks are useful too.
