set up logrotate upon receiving an apply message
use 50M as default MaxLogFileSize in apply message
use filepath.Join
Gracefully handle instances with no job_index

  * `bosh vms` no longer tries to look up instance based on a sequel filter
    that uses an empty string for an integer

Signed-off-by: Tony Hansmann <thansmann@pivotallabs.com>
Formatting

Signed-off-by: Tony Hansmann <thansmann@pivotallabs.com>