Fixes #7

Multiple search for initiation.

In he previous implementation, when search for initiations was activated, a spherical damaged zone was placed where Y was maximum and greater than Yc.

In this commit, a new parameter allow_multiple_seach was added, to place spherical damaged zones at each point where Y>Yc (set allow_multiple_seach to 1 to allow multiple search for initiations). The default value of this parameter is zero, so it should not change anything in the test cases.