Comments in protection tables

Protection tables can be difficult to interpret and debug. Including comments can make this work much easier.

You can append comments at the end of a line using the ## symbols:
```
write user *   10.1.1.1   //depot/test/...  ## robinson crusoe
```
Or you can write a comment line by prefixing the line with the ## symbols:
```
## robinson crusoe
write user *   10.1.1.1   //depot/test/...
```

Warning

Comments you have created using the P4Admin tool are not compatible with comments created using the 2016.1 version of p4 protect. You can use the following command to convert a file containing comments created with P4Admin into a file containing p4 protect type comments:

$ p4 protect --convert-p4admin-comments -o

Then save the resulting file.