Added new GPIO HAL function gpio_is_connected() used to check if gpio_t is connected or initialized with NC

Simple gpio_t structure in TARGET_KPSDK_MCUS field name changed to allign to other HALs
Added is_connected() method to Digital I/O classes APIs (DigitalIn, DigitalOut and DigitalInOut
Decorated all HALs with gpio_is_connected() function implementation
Added operator[] for BusIn and BusOut to add access to particular bit in random-iterator fashion
Added mask() function to BusIn and BusOut components

You can use BusIn::mask() or BusOut::mask() to get binary mask of all connected and NC pins in bus
Added operator[] and mask() function to BusInOut

This change follows changes in BUsIn and BusOUt API
Simple indent
Simple indent