! s and u tags could not be disabled in editor + construct is tidier

- changed if/else to array & foreach construct
- if/else had incorrect conditions anyhow since "i" was repeated in error
(more to come with this file since bbc button array is not working properly atm)

Signed-off-by: -Underdog- github.underdog@gmail.com
Maybe pass $disabled_AltTags into the hook? Rename it to $disabled_editor_tags?