[#54088489]

Had to regenerate this guide since the macro for build_an_application_subhead
was mended

Edit README.ftl.md and SIDEBAR.md

-Add build_an_executable_jar_subhead to README.ftl.md
-Revise Summary per language for other summaries
-Revise SIDEBAR.md per language for other Related Resources
-Revise "Understanding" to "Concepts and Technologies" per others

-Avoid excessive italics in README.ftl.md Looks jarring.
-In Summary section, suggest adding a link to Related Resources
(SIDEBAR.md) so reader doesn't have to scroll all the way back up page.
You don't want to put links in Summary because it's redundant and
Summary is about summing up current guide.
-Make Related Resources a main head, edit intro.

Making 'Related Rerources' title smaller in the sidebar

 - Add link to actual GSG
 - Add Tutorials section
 - Clean up Understanding section

Note, this was processed using the following command line:

    fpp --input=README.ftl.md --output=README.md

and output suffers from the bug detailed at:

    https://www.pivotaltracker.com/story/show/52221207

In *Create a main class* moved first paragraph of text to beginning of
section, before code.>>>>>>> upstream/master

- Change admonition style to use blockquote syntax