Add "check.linear_ode.R"

Add "check.linear_ode.R" to check following properties of
  the linear ODE system:
  correlation, VIF.
Modify "test.R".
Add "data.linear_ode.R"

Add "data.linear_ode.R" to export
  coefficient(sparse and full), intercept, observation matrix
  as data-files.
Modify "test.R".