Fix 'e.g.' and 'i.e.' usage in user-facing strings

The proper use of 'e.g.' and 'i.e.' are confusing and reportedly are one of the most frequent sources of mistakes editors see in technical writing/documentation. Drupal's user-facing strings include some examples of incorrect usage as well.

This issue is a "holding area" for strings that should be changed the next time such changes are permitted. These strings are then translated into various other languages so such changes need to be made with particular care.