Cope with missing bounds
Cope with missing climatology bounds.
update to handle up to 3 dimensional cube so that we call scoreatprecentile with
only upto 2d data.
Merge pull request #672 from rhattersley/missing-bounds

Cope with missing bounds
Merge pull request #625 from munslowa/percentile_agg

Percentile agg
added 42-byte wmo header, requiring code tidy