SDA + SCL: pin customization

[fritzen]

Motivation
This change was motivated by the incompatibility of ESP32-CAM hardware, which has no exposed sda / scl pins:

Changes

• Added sda and scl parameters for the begin method.
• Compatibility is maintained

Tests

• pwm.begin(255); //prescale - OK
• pwm.begin(2,14); //2=SDA, 14=SCL - OK
• pwm.begin(2,14, 255); //2=SDA, 14=SCL, 255=prescale - OK
• pwm.begin(); - OK

[ladyada]

will not merge

see: adafruit/Adafruit_BME280_Library#62
adafruit/Adafruit_MCP9808_Library#23
adafruit/Adafruit_BMP280_Library#38

please tell the ESP BSP supporters to add a function called, like, setPins() to Wire, because the official arduino Wire library does not allow what they have added

[fritzen]

Sure.. it`s incompatible with Arduino Wire.

I modified the code below to make it compatible with ESP32-CAM.

  #ifdef ESP32_CAM
        _i2c->begin(14,15);
  #else
        _i2c->begin();
  #endif

[ladyada]

this works for you but will be difficult to maintain for us :)