Fix the spelling of "optimize"
Clarify the usage of 'db_user' and 'omero_database'

...as discussed in devteam on the evening of 22 February.
Make instances of 'db_user' and 'omero_database' bold
Fix a typo
Fix the default values warning so that it is actually built
merge develop -D org -I include -E exclude: PR 297 (Upgrade page fixes (rebased onto develop))