Removed third part of the pinging wave.
Falling edges for distance calculation

Now the microcontroller exclusively only the falling edges for range
finding. Range is double.
Set a counter for maximum values to be sent to the master.
Now shows byte received if no acknowledgement is received.
Rewrite of main function loop of us_driver.

Rewrote the the main loop of us_driver so that it may only have to read
the the communication port once. This was done to reduce the places
where the program can get stuck waiting for the input. This will also
enable to implement resending of the configuration string in case
either:
-There is no input detected from the microcontroller.
-No ACK signal is detected over a long string of input data received.
Timeout detection using signals.
Listening sensor now checks for echo value only greater than that of the base value.
Watchdog Timer

Microcontroller now uses a watchdog timer to implement a timeout on
receiving configuration string from the master. Once any data byte is
received at the communication port, a watchdog timer of four seconds is
initialized. In case of failure, the microcontroller is restarted. Since
now the master also implements a timeout, it ensures that in case of any
communication line distortion, thecontroller board can be initialized
with the configuration string again.
Added handlers for shutdown to return the original values of serial port on program exit.
Removed sleep in main loop as it was causing loss of characters on the serial port.
Added the timestamp to the ExRange message.
If no acknowledgement is received within a range, the node would be shutdown.The launch file has a respawn flag which will detect shutdown of the node and will restart it. It will not restart if Ctrl-C is used to close it.
Microcontroller now sends a 16 bit data field after sending acknowledgement which specifies which sensors are connected and which are not. Handling code added in master as well.
us_driver node now parses sensor configuration in the beginning of a transmission and displays errors or warning based on its usage in the configuration file. In case timeout occurs ten times consecutively, node will restart. Now handles xmlrpc kill messages with a node restart.
Displays warning for unconnected sensors once.
If there is some problem in the connection after ack is received and 0x00 values are received, it will wait for hundred data bytes and then will restart.
Changed softuart buffer capacity to 48 bytes so accomodate config strings more than 15 configurations.
Merge branch 'master' of https://github.com/ipa-josh/ipa_lcrob
Added a boolean debug paramater in the launch file. User will have to enable it in the launch file. Will show debug messages on activation.
Added a message tonotfy when the messages are being generated.