Move the matrix-free project copy operation up the call stack.

Move the matrix-free project copy operation up the call stack.

The matrix-free projection solves the linear system with a specific vector type
and then copies the result into the given one. This commit moves that copy
operation into a separate function so that the actual matrix free function no
longer depends on the type of the input vector. Put another way: we no longer
have to instantiate the matrix free projections for all possible vector types.

Before moving the copy operation:
                                    File name Memory, MB    Time, s
      source/numerics/vector_tools_project.cc       2774         76
source/numerics/vector_tools_project_inst2.cc       2829         81
source/numerics/vector_tools_project_inst3.cc       2823         86

After:
                                    File name Memory, MB    Time, s
      source/numerics/vector_tools_project.cc       1855         47
source/numerics/vector_tools_project_inst2.cc       1995         51
source/numerics/vector_tools_project_inst3.cc       2183         55