Have gulp-tasks intelligently/lazily require modules

[jskrzypek]

There are a lot of tasks with a lot of requires at the moment. The required modules all load even if they are not used in any of the various tasks that will run. Since requiring modules is blocking, this adds a significant delay to running any task. We should be able to lazily make sure that modules are loaded just before the start of the first task that needs them, instead of the all at once thing.