Configure the pins as open-drain just in case the code forces them
high although it should be configuring them as inputs to let them float high.
Initialize the pins when the driver is initialized.
Enable the internal pull-ups to prevent them floating too high if not
connected and damaging the circuit.
This fixes a long-standing bug where build directories sometimes
expanded many levels deeper than they should have.
Component names can now no longer contains slashes (ie the component
name for 'extras/i2c' is now just 'i2c')
Fixed reference to unknown environment var
Moved drivers into extras folder and added additional documentations.
Changed LOCAL to static and renamed DEBUG to BMP180_DEBUG
