XAFORUM-142: Improve the Flag feature

I did this, because in Translations there were 7 reasons listed and in FlagClass the indexing was just from 1 to 6, so one reason was never displayed in the dropdown list.

I also changed the indexing in Translations, to begin from 0 and I also added a translation for the value "alt" : ForumCode.FlagClass_reason_7 = Other reason, because there wasn't one and that's why it was appearing "alt" as the last reason in the dropdown list.