Fixes for generic architectures. I2C address parameter. Refactoring

[imcatwhocode]

Full list of changes:

• Fixed _delay_ms() function for non-AVR and non-ESP8266 boards
• Add BH1750 I2C address defenition in constuctor (because the address may vary)
• Library code refactored. More clean legacy defines.
• Debug mode now can be enabled via #define BH1750_DEBUG in sketch
• Debug output now had prefix: [BH1750] ...
• Now, all modes constants enlisted in keywords.txt file as LITERAL1
• Modified Platform.io library manifest, because now library supports all kind of platforms with Arduino framework (see first paragraph in this list).
• Added library.properties file for Arduino Library Manager
• Little changes in README
• Add advanced usage example
• Use .ino sketch extension, instead of legacy .pde

[claws]

@CatWhoCode merged. Thanks for the cleanups.