Added name+units->lbfc definitions to replace Iris rules matching by name alone.

Added several new mappings to associate LBFC values with specific CF name+units.
This is to support the replacement of the old Iris text rules which set LBFC based only on cube names.
See 

**NOTE**:  a potential problem -- I was unable to use my own id to assign editor/ownership, as this does not seem to be supported by metarelate at present, so the new rules are credited to marqh.
If this (or anything else) needs to be amended, it may be necessary to revise the Iris pull request to ensure that um_cf_map.py exactly matches the current output from iris-code-generators.