Flake8 & isort

[scleakey]

• Code must conform to Flake8 & isort to get a green tick
• The following error codes are disabled globally:
  • E203 Whitespace before ':' (conflicts with black)
  • E402 Module level import not at top of file (licence is at top of file)
  • E501 Line too long (conflicts with black when it's a string)
  • W503 Line break occurred before a binary operator (W504 chosen instead)
• The following error codes are disabled for certain files:
  • F401 Module imported but unused (for __init__.py only)
• The following error codes are disabled inline:
  • C901 Function is too complex (for functions already with a complexity > 10)
  • N801 Class names should use CapWords convention (for FLAT_V_WEIR)
• I also deleted sample scripts which have since been turned into toolbox tools to avoid duplication

[scleakey]

Also if you approve this pull request, could you please not delete the branch if possible? It would be good to include mypy for type checking once I have time!