plume-util 1.8.0

• Deprecated Pair class for mutable pairs; use MPair instead.
  OrderedPairIterator uses MPair instead of Pair.
• New class IPair for immutable pairs.
• The WeakIdentityPair constructor is deprecated in favor of the of() method.
• New interface DeepCopyable.
• New methods in UtilPlume:
  • firstNonNull()
• New methods in CollectionsPlume:
  • for Collections: cloneElements(), deepCopy()
  • for Maps: cloneElements(), cloneValues(), createLruCache()