Many code blocks are 4spaced, and they render in GitLab
without coloring as a result, even though they are
fenced with a language label. If in a list, other items
will render as being in a code block too, even if not
meant to. This fixes all these issues, and cleans up
minor white space issues in install and integration docs
Use "Salesforce" (lowercase 'f')
Use Salesforce help doc language to navigate setup menu
Clarify to use callback url matching the GitLab installation url
