Improve pad placeholder behaviour

[atd]

See P2Pvalue/angular-swellrt#18

[atfornes]

P2Pvalue/angular-swellrt@da1ecf3 solves this. It does not hide placeholder on focus. However, if all text is erase, the placeholder does not appear again until a blur event occur.

I believe it is good enough behavior, and since it is difficult to consider the case previously exposed, I will close the issue whtih this fix. @atd, please open the issue again if you believe that it still needs to be fixed.

[atd]

@atfornes I agree that it is good enough. The main reason was to be able to focus the pad on new project creation, and still displaying the placeholder

However I would expect its behaviour to be consistent with other placeholders. So I would keep P2Pvalue/angular-swellrt#18 opened