docs: Add cross references in userguide

This patch adds necessary cross references to CBMC and Cppcheck
application note from build examples and getting started guides.
The contribution guide is also enhanced to add notes about static
analysis as part of the contribution workflow.

Some minor corrections are also made in the cppcheck application
note.

Signed-off-by: Soby Mathew <soby.mathew@arm.com>
Change-Id: I67fe84b154f14dd49152862b5bdd4402ddb88881
4 files changed