Add arduino code for bluetooth support.

[dipu989]

Fixes #306

Changes:
Added Arduino code for Bluetooth support.

Checklist: [Please tick following check boxes with [x] if the respective task is completed]

• I have used resources from strings.xml, dimens.xml and colors.xml without hard-coding them
• No modifications done at the end of resource files strings.xml, dimens.xml or colors.xml
• I have reformatted code in every file included in this PR [CTRL+ALT+L]
• My code does not contain any extra lines or extra spaces
• I have requested reviews from other members

APK for testing:
NA

[dipu989]

@mariobehling @jddeep @CloudyPadmal @adityastic
Please check if the logic I have written is what we expect from the app.

[CloudyPadmal]

Did you test this on real devices? Shouldn't the USB function use Serial while the Bluetooth one uses SoftwareSerial?

[dipu989]

@CloudyPadmal After Bluetooth module's getting connected, it was unable to receive instructions for switching between different modes. I opened the PR to get the mistake pointed out and verify that the code that I have written is according to the expected logic or not!