Add support no boolean keys in tweaks
Add "Maximum tab width" tweak (#235)
Change panels style (#249)

Needs for correct work on systems without X compositor.
Tweaked 'page' icon
Added 'sidebar' icon (#79)
Export sidebar icon to symbolic-icons/sidebar.svg (#79)
Rename gtranslator.svg to translate.svg (#79)
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Merge branch 'master' into preprocessor
Changed icons of #sidebar-button and #translate-notification-icon buttons