UI config to toggle whether user email shows up in Explore Users (#336)

* UI config to toggle whether user email shows up in Explore Users

* Recommendation made by @tboerger
https://github.com/go-gitea/gitea/pull/336/commits/66a1c59fe730eff019ce100673c6800cce7d102d#r94122732

* fixed typo, rename ShowUserEmailInExplore to ShowUserEmail

* Fixed typo merged conflict

* Hide email in the user profile page

if you are active ShowUserEmail
ref https://github.com/go-gitea/gitea/pull/336#issuecomment-269843725

* Please replace MustBool() with MustBool(true)

templates/explore/users.tmpl

@@ -16,7 +16,7 @@
 									{{if .Location}}
 										<i class="octicon octicon-location"></i> {{.Location}}
 									{{end}}
-									{{if and .Email $.IsSigned}}
+									{{if and $.ShowUserEmail .Email $.IsSigned}}
 										<i class="octicon octicon-mail"></i>
 										<a href="mailto:{{.Email}}" rel="nofollow">{{.Email}}</a>
 									{{end}}

templates/user/profile.tmpl

@@ -22,7 +22,7 @@
 							{{if .Owner.Location}}
 								<li><i class="octicon octicon-location"></i> {{.Owner.Location}}</li>
 							{{end}}
-							{{if and .Owner.Email .IsSigned}}
+							{{if and $.ShowUserEmail .Owner.Email .IsSigned}}
 								<li>
 									<i class="octicon octicon-mail"></i>
 									<a href="mailto:{{.Owner.Email}}" rel="nofollow">{{.Owner.Email}}</a>