Support RTL (Right-to-Left) languages and layouts

Is your feature request related to a problem? Please describe.

There are multiple RTL/BiDi languages in the world. Using them often requires also the matching layouts. Qt allows creating interfaces that play well with those layouts (see links below).

Describe the solution you'd like

Currently Cutter has some (but incomplete) RTL languages translations, but they all require RTL/BiDi-friendly layouts. We should support them out of the box:

• Urdu (unimplemented)
• Arabic (complete translation is available)
• Persian (incomplete)
• Hebrew (incomplete)

Describe alternatives you've considered

Additional context

• https://stackoverflow.com/questions/36295725/getting-qt-layout-direction-to-use-right-to-left-features-e-g-for-arabic-in-c
• https://community.kde.org/KDE_Localization/RTL
• https://github.com/owncloud/client/issues/8806