[CB-3849] reveal xrefs to Platform Guides
[CB-4204]: minor doc improvement

Clarify that the "src" attribute should be used on the <content> element to set its value.
[CB-3962] Add to style sheet.
[CB-3962] Change 'IDE' to 'SDK'.
[CB-3962] Change 'simulator' to 'emulate'.
[CB-3962] em dashes and bulleted topics.
[CB-3962] Removed unnecessary subheads.
Removed hidden ripple content for good.
[CB-4224] updated wp docs for 3.0.0