Version 2.0.0

New features:

• Handle statistics on selectivity estimation errors (Julien Rouhaud, per
  idea from Oleg Bartunov)
• Add an index advisor feature (Julien Rouhaud)
• Allow pgqs to work locally without being in shared_preload_libraries (Julien Rouhaud)

Bugfix:

• Fix handling of quals of the form Constant Operator Val where the
  operator doesn't have a commutator
• Compute the same identifier whether the operator was commuted or not
• Correctly discard all quals not referencing a relation
• Fix (unique)qualid computation to only consider AND-ed quals

Miscellaneous:

• Add missing fields description (Julien Rouhaud)