pwm_p_decode (OOK_PWM_P) first bit bug fix

Fixes #67 pwm_p_decode (OOK_PWM_P) first bit bug

There is a bug processing the start bit that causes the first real bit (2nd pulse) to be misinterpreted unless the long_limit is higher than the long pulse period (long pulse width + space width * 2). The sample_counter isn't reset after processing the start bit, which makes it look like the long_limit was reached when it shouldn't have been. Note: Setting the long_limit high enough will work around this bug.