moved interface code out from solver

src/interfaces.jl

@@ -0,0 +1,24 @@
+# This file is a part of JuliaFEM. License is MIT: https://github.com/ovainola/JuliaFEM/blob/master/README.md
+module interfaces
+
+using Logging
+@Logging.configure(level=DEBUG)
+
+VERSION < v"0.4-" && using Docile
+
+#using JuliaFEM.elasticity_solver
+export solve_elasticity_interface!
+
+@doc """
+This is generic interface that reads data from data model, solves elasticity
+problem and updates model.
+
+Parameters
+----------
+model : to be defined
+""" ->
+function solve_elasticity_interface!()
+  return 0
+end
+
+end