Don't include <iostream> in tester.

It is not needed and was only added for convenience during test
development.
Add stub test for ADB::operator+()

Doesn't actually test anything at the moment.
Implement a custom comparator for Eigen::SparseMatrix<double>

Use it to simplify the 'FunctionInitialisation' test.
Add test for addition of ADB::variable()s.
Merge remote-tracking branch 'atgeirr/master'
Don't require initialiser lists.

These were introduced into GCC as recently as edition 4.7 .  Ubuntu
10.04 LTS features GCC 4.4 only.