Imports of package unification

PathSynopsis
contextPackage context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
github.com/purpleidea/mgmt/lang/interfacesPackage interfaces contains the common interfaces used in the mcl language.
github.com/purpleidea/mgmt/lang/typesPackage types provides a framework for our mcl language values and types.
github.com/purpleidea/mgmt/utilPackage util contains a collection of miscellaneous utility functions.