Compute unit requirement strings

When a job is submitted with compute unit resource requirements, any requirements apply only to the execution cluster. Only the syntax of the resource requirement string is checked on the submission side, and if the cu[] string is valid, the job is forwarded.

When compute unit requirements cannot be satisfied in the remote cluster (such as a non-existent compute unit type) jobs may be rejected by the remote cluster. Hosts running LSF 7 Update 4 or earlier cannot satisfy compute unit resource requirements.