Added missing GLUE2 attributes and max/defaults values.

- GLUE2ComputingShareMaxMainMemory (rss)
- GLUE2ComputingShareMaxVirtualMemory (vmem)
- GLUE2ComputingShareMaxSlotsPerJob (and GLUE equivalent)
- GLUE2ComputingShareDefaultWallTime
- GLUE2ComputingShareDefaultCPUTime
- GLUE2ComputingShareMaxTotalJobs
- GLUE2ComputingShareMaxWaitingJobs
Merge pull request #6 from ge-utils/add_glue2_missing_attributes

Added missing GLUE2 attributes and max/defaults values.