Time of transmission

In the current version of iHOP, the time of transmission **MUST** align with the time of an MITgcm iteration. There is no code for transmission of acoustic sound propagation in between gcm time steps.

Example:
```
# from data namelist:
nIter0 = 0
deltaTClock=1000.
```
iHOP sound transmission can only be at 1000 seconds, and not 500 seconds. 