Ordering/grouping keywords in deck

[koubaa]

Works for me.

Maybe related: would it be useful to be able to combine/split several databases as well?

control_db = db.DB()

control_db.append( keywords.ControlImplicitSolution() )



mesh_db = db.DB()

mesh_db.append( keywords.ElementSolidOrho() )



combined_db = db.DB()

combined_db.combine( control_db, mesh_db ) 



dbs = combined_db.split_by_category()

Mainly interested since I typically tend to write out these kind of categories to individual .k files:

main.k

parts.k

nodes.k

segment_sets.k

boundary_conditions.k

...

Some high level methods to manipulate these databases may be helpful for the user.

Originally posted by @mhoeijm in #606