Various cleanups

[claws]

• Update link to Data Sheet in BH1750.h file to be same as in README.
• Fix code comments:
  • fix spelling errors
  • wrap longer lines
  • add a space between comment char and comment.
• Fix some code formatting (no functional change).
• Fix some console output text in example script.
• Update Travis automated CI:
  • display all compiler warnings
  • verify all examples
• Update local builder script
  • display all compiler warnings
  • Show a ✔️ or ✖️ tick status based on return code.