feature/#507 Implement autoarrange

[Ivanruii]

Implement autoarrange collection and animation when adding a new collection.

Demo gif:

Closed #507

[brauliodiez]

Seems not to be working, just loaded the sample database model and instead of finding an empty gap it just places the collection in the middle of the view zone:

[Ivanruii]

Seems not to be working, just loaded the sample database model and instead of finding an empty gap it just places the collection in the middle of the view zone:

It is fixed.

[brauliodiez]

General feedback:

Add more gap when adding a new table, the idea is that you can add two tables and add a relationship between them, right now is too tight

Double the gap size

[brauliodiez]

General Feedback:

missing the simple animation higlighting / blinking temporarily the table that has been added