moved purely "array" related stuff to a new module Array.

This include:
 - cwise Pow,Sin,Cos,Exp...
 - cwise Greater and other comparison operators
 - .any(), .all() and partial reduction
 - random

Eigen/src/Array/CMakeLists.txt

@@ -0,0 +1,6 @@
+FILE(GLOB Eigen_ARRAY_SRCS "*.h")
+
+INSTALL(FILES
+  ${Eigen_ARRAY_SRCS}
+  DESTINATION ${INCLUDE_INSTALL_DIR}/Eigen/src/ARRAY
+  )