Convert gn docstrings to C++11 raw strings.
This makes them more readable and easier to modify.
The documentation was un-indented and re-wrapped to 80 cols which makes it fill out the column on the screen better.
A few tests were updated to use raw strings as well, but converting all of them seemed not worth the effort.
There is a documentation fix in the set_defaults (added [] around the configs in the example), and an obsolete line in the group documentation was removed ("exactly like depending on its deps).
Review-Url: https://codereview.chromium.org/2481423002
Cr-Commit-Position: refs/heads/master@{#430679}
38 files changed
