Add SALOME 5.1.5 release notes

diff --git a/SALOME_5_1_4_Release_Notes.pdf b/SALOME_5_1_4_Release_Notes.pdf
deleted file mode 100755 (executable)
index e4982e9..0000000
Binary files a/SALOME_5_1_4_Release_Notes.pdf and /dev/null differ

diff --git a/SALOME_5_1_5_Release_Notes.pdf b/SALOME_5_1_5_Release_Notes.pdf
new file mode 100755 (executable)
index 0000000..aa3d33f
Binary files /dev/null and b/SALOME_5_1_5_Release_Notes.pdf differ