Change maximal pt in calculation of b-tagging scale factors

New b-tagging scale factors (EPS'13) are defined on a larger pt domain.
This commit should have entered 3.3.4 but missed it.
Add defaults for generators in class Dataset
Allow more than one process code in an instance of Dataset
Update process codes in Dataset

Some of existing codes are renamed which will break backward
compatibility.
Add move and copy constructors and assignment operator to Dataset
Add ordering of process codes in Dataset constructor
Optimise forwarding of process codes in Dataset
Add to Dataset convenience methods to access process codes
Add an interface to access b-tagging efficiencies

The commit prepares a resolution of issue #13.
Add a generic class to access b-tagging efficiencies

The update addresses issue #13.
In BTagEffInterface, do not allow to override efficiency accessor with
default working point
Add a class describing interface to access b-tagging scale factors
Fix bug in constructors of BTagEfficiencies

The copy and move constructors and the assignment operator ignored the
base class.
Rename nominal variation is BTagSFInterface
Add a specification of pseudorapidity domain to BTagSFInterface
Add a specialised class to access b-tagging scale factors

Scale factors are hard-coded and follow recommendations for EPS'13. The
commit addresses issue #13.
Allow a symultaneous usage of several working points in BTagger
Explicitly define copy and move constructors and assignment operator in
BTagger
Change BTagEfficiencies to access the efficiency by signed jet
pseudorapidity instead of an absolute value.
Add a ROOT file with efficiencies in the new format

File created by Afiq. Efficiencies are measured in the pretag region of
tH(bb)q analysis and provided as an example only.