Fix "AVR910" typos to "AVR109".
Use spaces instead of tabs where necessary to fix indentation.
Use spaces instead of tabs wherever necessary to fix indentation.
Minor formatting fixes.
Merge branch 'mondalaci-avr910_typos'
Merge pull request #7 from mondalaci/hidclassdevice_whitespaces

Use spaces instead of tabs where necessary to fix indentation.
Extract interface numbers into enums.
Merge pull request #8 from mondalaci/extract-interface-numbers

Extract interface numbers into enums.
Minor documentation corrections.