JustifyCenter added into psui-contenteditable

New functionality in psui-contenteditable.

Signed-off-by: Pavol Starek <pavol@starek.sk>
psui-selectbox implemented [#71674902]

Implementation of psui-selectbox and separation of
dropdown functionality into separate factory.

[FINISHED #71674902]
Small visual fix in psui-autocomplete

Fixed default value of dropdown.