New API support

Changes

• Adjusted to the new version of API (#72)
• Added reading current readings (#6)
• Added support for all tariffs (#10, #40, #46)
• Improved handling missing data (#22)
• Added returning date of daily data (#41)
• Added hourly balancing (#57)
• Fixed usage of deprecated code (#70)
• Increased pulling interval (#71)
• Added support for diagnostics

Breaking changes

• Removed check_generation flag from YAML config - integration relies now only on monitored_variables
• Removed zone from monitored_variables - automatic detection of current zone is no longer available