[LocationBar] Make sure text format is correct even when text doesn't change

refreshTextFormat() is using page's url to determine which part of
displayed text is host. Url of page may not change immediately when
starting loading.
This commit makes sure that text format is correct with every
WebView::urlChanged() signal.
[LocationBar] Fixed showin progress over text. Use opacity with QPainter

Not the best solution, but probably the easiest.
Closes #1261
[Themes] Fix loading linux.css and mac.css on Mac/Linux
[ComboTabBar] Set objectName of base widget, so it can be styled

TabBar base is now correctly styled in all themes.
Updated the themes accordingly to this change.