Dialog Message bugs and consistency

[saulgreenberg]

• various uses of DialogMessage does not have the owner assigned, which causes a failure when a later (new) method tries to reposition the window
• DialogMessage variable sometimes called dlgMsg, and other times MessageBox (very minor, but use same name for consistency)

[saulgreenberg]

Fixed.

• Owner is now set before the dialogbox is shown
• renamed messagebox to DlgMsg
• SetDefaultDialogPosition now aborts setting Left and Top if the owner is null