Always center dialog before reopen

[huineng]

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Current behavior
dialog not centered

Expected behavior
call this.center();

What is the motivation / use case for changing the behavior?
I'm reusing the dialog to open various modals with different widths, center() is not being called

Please tell us about your environment:

• Angular version: 2.4.0

• PrimeNG version: 2.0.3

I'm reusing the p-dialog to display various content in various sizes, the p-dialog is not destroyed
content is dynamically changed

this works nicely except that for each "other then the first" the window is not centered
because of this in your code

if(!this.positionInitialized) {
            this.center();
            this.positionInitialized = true;
        }

This "this.positionInitialized" is updated only once and cannot be changed anymore
means if i reuse the component this values is never reset and thus the window is not centered

if it possible to either
turn positionInitialized into an @input public positionInitialized: boolean || false

or remove that line (not sure why it's there even )
or any other suggestion

thanks