Project restructuring / reorganization

[clarity20]

The newest needs along this line:

• The SQL construction loops & their helper functions should have their own source file
• Factor out a new source file for higher-level clause builders (clause_functions ?)
• Consider stripping down db_functions even further
• db_functions should be renamed core_functions
• Is _functions the best naming convention for code libraries? Consider something 'lib'-bish
• Introduce a more conventional directory structure:
  • test
  • scripts or bin
  • lib as mentioned above
  • etc.