Add documentation for gulp tasks using gulp-help

[waldekmastykarz]

As the number of gulp tasks and their complexity increases it would be helpful to have documentation that not only lists the available tasks but also shows the different parameters that can be used if applicable. We could do this for both generator's and generated tasks using gulp-help.

[beth-panx]

As we moved away from gulp tasks and implemented Browsersync. This is no longer needed.