pmempool info: printing info about many pool files

[kkajrewicz]

It would be nice if printing info about many files would be possible. It can be useful especially when comparing information about many parts of the same pool.

e.g. at now we have to call pmempool info X times to print info about X files: $pmempool info pool.part1 $pmempool info pool.part2

Following call results in printing info about first pool file only: $pmempool info pool.part1 pool.part2

Consider concatenating files before printing on stdout (as unix's CAT(1) does).