Pull Request for Issue1110: add flag for AMSelectionDialog to control whether allows empty selected items

-- Added: emptySelectedItemsAllowed feature for AMSelectionDialog. With this flag, if empty selected items is not allowed and no items are selected, then the Okay button will be greyed out. 
-- add compile setting to AMCommon.pri, so that all the files (.obj, moc_, ui_) generated by compiler will be stored in corresponding folders instead of the root folder

https://github.com/acquaman/acquaman/issues/1110

@dretrex @davidChevrier 
@davidChevrier @dretrex with this changes, all the obj files, moc_ files and Ui_ files will put in the corresponding folders instead of under ./acquaman/.

I think this will make the folder clearer. Please let me know if you are ok with this or not. Thanks