Add formspec toolkit and refactor mainmenu to use it

Fix crash on using cursor keys in client menu without selected server
Add support for non fixed size tabviews

builtin/mainmenu/dlg_rename_modpack.lua

@@ -0,0 +1,69 @@
+--Minetest
+--Copyright (C) 2014 sapier
+--
+--This program is free software; you can redistribute it and/or modify
+--it under the terms of the GNU Lesser General Public License as published by
+--the Free Software Foundation; either version 2.1 of the License, or
+--(at your option) any later version.
+--
+--This program is distributed in the hope that it will be useful,
+--but WITHOUT ANY WARRANTY; without even the implied warranty of
+--MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--GNU Lesser General Public License for more details.
+--
+--You should have received a copy of the GNU Lesser General Public License along
+--with this program; if not, write to the Free Software Foundation, Inc.,
+--51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+--------------------------------------------------------------------------------
+
+local function rename_modpack_formspec(dialogdata)
+	
+	dialogdata.mod = modmgr.global_mods:get_list()[dialogdata.selected]
+
+	local retval =
+		"size[12.4,5,true]" ..
+		"label[1.75,1;".. fgettext("Rename Modpack:") .. "]"..
+		"field[4.5,1.4;6,0.5;te_modpack_name;;" ..
+		dialogdata.mod.name ..
+		"]" ..
+		"button[5,4.2;2.6,0.5;dlg_rename_modpack_confirm;"..
+				fgettext("Accept") .. "]" ..
+		"button[7.5,4.2;2.8,0.5;dlg_rename_modpack_cancel;"..
+				fgettext("Cancel") .. "]"
+	
+	return retval
+end
+
+--------------------------------------------------------------------------------
+local function rename_modpack_buttonhandler(this, fields)
+	if fields["dlg_rename_modpack_confirm"] ~= nil then
+		local oldpath = core.get_modpath() .. DIR_DELIM .. this.data.mod.name
+		local targetpath = core.get_modpath() .. DIR_DELIM .. fields["te_modpack_name"]
+		core.copy_dir(oldpath,targetpath,false)
+		modmgr.refresh_globals()
+		modmgr.selected_mod = modmgr.global_mods:get_current_index(
+			modmgr.global_mods:raw_index_by_uid(fields["te_modpack_name"]))
+			
+		this:delete()
+		return true
+	end
+	
+	if fields["dlg_rename_modpack_cancel"] then
+		this:delete()
+		return true
+	end
+
+	return false
+end
+
+--------------------------------------------------------------------------------
+function create_rename_modpack_dlg(selected_index)
+
+	local retval = dialog_create("dlg_delete_mod",
+					rename_modpack_formspec,
+					rename_modpack_buttonhandler,
+					nil)
+	retval.data.selected = selected_index
+	return retval
+end