BUG: Fixed exclusion list

Currently iris test coding standards will perform pep8 checks on files
contained within the build directory and then ignore the results.  This
commit removes this checking entirely and fixes a bug present in
generating the assumed directory for the iris repository from the iris
path (a problem which arises when considering softlink vs real paths).
Reorder GRIB/CF map entries.
Proposed addition to allow categorisation of 2D coords
Review actions
Default LBUSER(2) to -99 when saving to PP
tests around bounds, and messages on DimCoord constructor errors
pp rules
Fix docs for COUNT and PROPORTION aggregators.
grib rules
results
modify documentation of cube constructor to reflect a wider range of data types
unit tests
Merge pull request #866 from rhattersley/pp-lbuser2

Default LBUSER(2) to -99 when saving to PP
Merge pull request #867 from rhattersley/fix-count-docs

Fix docs for COUNT and PROPORTION aggregators.
Merge pull request #865 from jkettleb/bounds_doc

Documentation clarifying shape of bounds, adding tests to verify expected behaviour
Add units support to Aggregators.
nicer test
Merge pull request #862 from jkettleb/doc

Small modification to documentation around cube constructor
more robust hours calc
Merge pull request #861 from dkillick/coord_cat_2d

Categorisation of multi-dimensional coords.