Add files via upload

[keesma]

Added support for BMP280 (based on BME280)

[luebbe]

Thanks for your contribution.
One question: Is the BME280 an "extension" of the BMP280? I always thought so, but neve checked, because I don't have a BMP280.
In this case we could inherit the BME280 from the BMP280 (or create a common BMx280 base class) and save a lot of duplicate code.
Do the BME and BMP even share the same I2C addresses?

[keesma]

The BME280 also measures humidity. The other functions are the same. There is a different underlying library from Adafruit. The I2C addresses are the same but the device type is different. I am not sure what the best way is handling duplicate code. I used the BME280 code as a base and made some adjustments. While using it I noticed that the BMP280 cannot do forced measurements. I might have to provide updated source code for this.

[luebbe]

There is a lot that can go into a common base class when I look at the code. I'll let you finish your PR and afterwards I'll refactor.
I'm also thinking about making the sensor nodes more generic. loop() is basically always the same, only taking the measurement differs.