Elaborated on the handle/concept design principle

Updated the README. Hopefully the design of CxxDBC will be
slightly easier to approach from zero context.
Merge branch 'ruoso-master'
Split the connection helpers into their own header

Also did some renaming in the hopes that the purpose of the
types is more clear.
Split the statement helpers into their own header

Also did some renaming in the hopes that the purpose of the
types is more clear.
Split the result set helpers into their own header

Also did some renaming in the hopes that the purpose of the
types is more clear.
Split the result set meta helpers into own header

Also did some renaming in the hopes that the purpose of the
types is more clear.
Merge branch 'separate_concept_header'