add tmpdir option to callpeak and unify the output options

Hi Tao,

is something like that pull-request acceptable for you?
It adds the following:

1. adding --tmpdir to callpeaks
2. adding --ofile to bdgbroadcall, bdgcmp, bdgdiff, bdgpeakcall, refinepeak
3. adding --o-prefix and --ofile to bdgcmp to make it more consistent
4. for randsample and Co. I also added --ofile as alias for -o to be more consistent

Cheers,
Bjoern