Check project/client name to avoid duplicates. closes #331

Added a simple method to check if name is valid at the moment of save, if not, show a warning message. 
Joey's implementation is missing and probably will have to wait for "material" re-design. 

fixes #331
On Android the save-guard makes no sense, as the dialog is dismissed the moment the synchronous execution of this method ends. (I didn't realise that when I wrote the code.. in some places I think I even removed the save guard pattern.) Thus there is really no point in showing an error either as the item does exist already.

So, on android we can just safely continue doing what you are doing here: just act as if everything went smoothly.