Lhasa: Properly implement rendering of paths and arcs

[hgonomeg]

Tasks

• [x] Paths
  • [x] Figure out how cairo wraps those
  • [x] Replicate the same thing
  • [x] Redesign paths - current design is broken (impossible to make fills work in the frontend)
  • [x] Come up with a new design
  • [x] Implement it
  • [x] Reimplement cairo calls
• [x] Arcs - do I need to change anything in C++? - Yes, styling support. Part of Paths.

[hgonomeg]

All nicely done.