Copter: Change loop to 200 Hz
PRU: add PRU PWM code to Linux_HAL_Essentials
PRU PWM:Add usage steps for PRU firmware to Readme
Startup script:add reloading pru firmware option
Linux_HAL_Essentials: cleanup PWM PRU code
change firmware name to pwmpru1
PRU: remove obsolete libraries/AP_HAL_Linux/PRU
Linux HAL Readme:change firmware name to pwmpru1