Add submodule for INA219 driver.
Add power plant sample code to measure the current with INA219.
Add datasheet of ina219 and ina226.
Add submodule for INA226 driver.
Add sample code to measure the current & voltage with INA226.
Modify unit of current from mA to A.
Define slave addresses.
Merge branch 'issue_5' to fix issue #5.