Fixing main window size issues and craching on OSx

[oleg68]

Resolves: #68
Resolves: #71
Resolves: #72

• Now the main window size is set correctly if it was not saved with the organ settings Main Window not completely visible #71
• The main window can be resized manually and it's size and position is stored by Save menu entry
• If there are no organ open then the size and the position is saved on exit from the Setting dialog
• There is still a problem with sizing in MacOs Weird "menu" in main bar .. #72 caused a wxWidget/Osx bug. But now there is a workaround: enlarge this window manually and save the new size
• Refactored working with audio meters; the old one caused a crash on OSx when exit Crash on OSx #68