appview/pages: use queryParams func to build pagination URLs; wrap in safeUrl

when constructing a url using url.Values.Encode, we need to avoid
escaping the `=` symbol, which is performed by the default urlescaper
behavior in href contexts; so we wrap the call with safeUrl.

Signed-off-by: oppiliappan <[e-mail]>

appview/pages/templates/fragments/pagination.html

···
 {{ define "fragments/pagination" }}
-  {{/* Params: Page (pagination.Page), TotalCount (int), BasePath (string), QueryParams (string) */}}
+  {{/* Params: Page (pagination.Page), TotalCount (int), BasePath (string), QueryParams (url.Values) */}}
   {{ $page := .Page }}
   {{ $totalCount := .TotalCount }}
   {{ $basePath := .BasePath }}
-  {{ $queryParams := .QueryParams }}
+  {{ $queryParams := safeUrl .QueryParams.Encode }}
 
   {{ $prev := $page.Previous.Offset }}
   {{ $next := $page.Next.Offset }}

appview/pages/templates/repo/issues/issues.html

···
         "Page" .Page 
         "TotalCount" .IssueCount 
         "BasePath" (printf "/%s/issues" .RepoInfo.FullName)
-        "QueryParams" (printf "state=%s&q=%s" $state .FilterQuery)
+        "QueryParams" (queryParams "state" $state "q" .FilterQuery)
     ) }}
   {{ end }}
 {{ end }}

appview/pages/templates/repo/pulls/pulls.html

···
           "Page" .Page 
           "TotalCount" .PullCount 
           "BasePath" (printf "/%s/pulls" .RepoInfo.FullName)
-          "QueryParams" (printf "state=%s&q=%s" .FilteringBy.String .FilterQuery)
+          "QueryParams" (queryParams "state" .FilteringBy.String "q" .FilterQuery)
       ) }}
     {{ end }}
 {{ end }}