Add lagged information set in VAR based expectations.

matlab/+var_expectation/update_parameters.m

matlab/print_equations.m

matlab/write_expectations.m

tests/Makefile.am

tests/var-expectations/1-with-time-shift-a/example1.mod

tests/var-expectations/1-with-time-shift-b/example1.mod

tests/var-expectations/2-with-time-shift/example1.mod

tests/var-expectations/3-with-time-shift/example1.mod

tests/var-expectations/3/example1.mod

tests/var-expectations/4-with-time-shift/example1.mod

tests/var-expectations/5-with-time-shift/example1.mod

tests/var-expectations/6-with-time-shift/example1.mod

tests/var-expectations/6-with-time-shift/substitution.mod