Clean up various use of escape/unescape functions for URL generation (#6334)

* Use PathUnescape instead of QueryUnescape when working with branch names

Currently branch names with a '+' fail in certain situations because
QueryUnescape replaces the + character with a blank space.

Using PathUnescape should be better since it is defined as:

// PathUnescape is identical to QueryUnescape except that it does not
// unescape '+' to ' ' (space).

Fixes #6333

* Change error to match new function name

* Add new util function PathEscapeSegments

This function simply runs PathEscape on each segment of a path without
touching the forward slash itself. We want to use this instead of
PathEscape/QueryEscape in most cases because a forward slash is a valid name for a
branch etc... and we don't want that escaped in a URL.

Putting this in new file url.go and also moving a couple similar
functions into that file as well.

* Use EscapePathSegments where appropriate

Replace various uses of EscapePath/EscapeQuery with new
EscapePathSegments. Also remove uncessary uses of various
escape/unescape functions when the text had already been escaped or was
not escaped.

* Reformat comment to make drone build happy

* Remove no longer used url library

* Requested code changes

routers/home.go

@@ -7,7 +7,6 @@ package routers
 
 import (
 	"bytes"
-	"net/url"
 	"strings"
 
 	"code.gitea.io/gitea/models"
@@ -48,7 +47,7 @@ func Home(ctx *context.Context) {
 		} else if ctx.User.MustChangePassword {
 			ctx.Data["Title"] = ctx.Tr("auth.must_change_password")
 			ctx.Data["ChangePasscodeLink"] = setting.AppSubURL + "/user/change_password"
-			ctx.SetCookie("redirect_to", url.QueryEscape(setting.AppSubURL+ctx.Req.RequestURI), 0, setting.AppSubURL)
+			ctx.SetCookie("redirect_to", setting.AppSubURL+ctx.Req.RequestURI, 0, setting.AppSubURL)
 			ctx.Redirect(setting.AppSubURL + "/user/settings/change_password")
 		} else {
 			user.Dashboard(ctx)