Fix memory leaks in Petra_Converters*.cpp.

1. ST and LO raw arrays were being allocated, but Epetra_CrsMatrix/ MultiVector
do that, so (a) the alloc is unneeded and (b) the pointers are reassigned, thus
leaking the unneeded memory. (There was no delete[] in any case, which in fact
would cause a seg fault.)

2. Changed some ExtractCopy()s to ExtractView()s.