__StringFromFile enhanced to restart the reading when the loop of n files is reached

**fabien.levacher** ([Bug 60861](https://bz.apache.org/bugzilla//show_bug.cgi?id=60861&redirect=false)):
__Stringfromfile allows developers :
- to define the reading of one file with a restarting when the end of file is reached
- to define the reading of n files stored in a directory using to regex "_#" applied on the name file. n defines finally the number of loop. When n is reached , the thread is stopped ( end of sequence ) and finally the load test is stopped.

Can you add a new parameter to the function to allow developper to restart the reading after the reading of the last file ?

OS: All