[FEATURE] Use OpenLayers.Popup

1) instead of AttributeTree (fixes #7110)
2) instead of ExtJS.ToolTip (fixes #6452)

Style contents of ClickPopup with popup.css.
Disable HoverPopups when a ClickPopup has been opened.
Style mouse cursor in FeatureInfo-mode as default.
Change mouse cursor to type "pointer" as soon as
any FeatureInfo is received.
Remove obsolate translations.