Improved serial output & cleaned up code

[tobozo]

• Improved serial output (less spammy)
• Introduced ether_ntoa from Android
• Reduced memory fragmentation during rendering
• Refactored draw functions
• Fixed some typos and indentation
• Fixed accidental channel hopping with M5Core2
• Made channel hop mode as a preference

[G4lile0]

Great improvements @tobozo ! Thanks a lot for your work!