Add HashTree data structure with several functions. See commit message for all changes

[ByronBecker]

• Add HashTree data structure with init(), initPresized(), get(), put(), replace(), delete(), remove(), and equal()
• Add HashTreeMatchers
• Modify Entity.createEntity function, add Entity.equal and Entity.toText functions
• Create refactor common test setup functions into TestHelpers
• Add RangeTree.remove() function
• Add previously deleted test to RangeTreeTest
• Update StableHashMap version in package-set.dhall to include fix to FunctionalStableHashMap.size()
• Add several TODOs