Fixed typo

Corrected the typo on the word "Unexpectedly" (Previously "uexpectidly")
Remove new RegardingUserID when merging activity items

This is the correct PR for #1776
Merge pull request #2114 from hgtonight/patch-2

Remove new RegardingUserID when merging activity items
Make the mentions url format overridable.

Make the mentions url format a static property on Gdn_Format so that plugins can change it. This is necessary when user profile links are overridden.
Merge pull request #2097 from SudoCat/patch-1

Fix a typo on the entry connect page.
Merge pull request #2117 from vanilla/hotfix/mentions-format-string

Make the mentions url format overridable.
Merge branch 'master' into stage