Modify Picard and Bwamem memory handling
add some convience methods to check proximity of soft/hard limits
make has_space also check used_kb to reduce rollbacks due to over_used
convert debug_message to Genome::Logger

Convert debug_message to Genome::Logger so that they go to logstash.
add metric to record the number of attempted volumes
add cached_unallocated_kb and use instead of unallocated_kb
update allocated_kb to also return allocation count in list context
add method to dynamically define proximity to soft limit
use is_near_soft_limit instead of is_over_soft_limit

To avoid allocations "flapping", i.e. create and rollback, when volumes
are approaching soft limit we will disable them when they get "close
enough".