rework Beremiz application "testCheckProject" test to allow easier reuse later

add application name for PLCOpenEditor

This is needed to work user configuration load/store, if PLCOpenEditor
is launched from test environment.

rewrite PLCOpenEditor. Add PLCOpenEditorApp class for easier customizations.

lazy locale initialization

wx.Locale() can't be called without wx.App. So don't call it at
import. It makes PLCOpenEditor simpler.