* add before-you-begin-egress boilerplate and use it in one case
* move the boilerplate into content
* replace before-you-begin section for egress task/examples
* remove egress related details from the boilerplate
- The width value now defaults to 100%, so it doesn't need to be specified explicitly
in many cases.
- The ratio value can now be computed automatically for PNG and JPG files, so it doesn't need
to be specified explicitly.
Vadim Eisenberg
Martin Taillefer
Frank Budinsky