***.Calc(): display calculation time

Display time `***.calc()` took?
eg. `Device.calc()`, `Cavity.calc()`, `WG.calc()` etc.

The code to do this is as follows (python 2.5):

```
import time, date time
start = time.time() # get current time

### runCalc_function()

# print elapsed solving time:
print(  "Calc() took (h:m:s.us) :" + str(datetime.timedelta(seconds=time.time()-start))   )
```
