lox-frames-v0.1.0-alpha.4

Added

• (lox-units) add Keplerian elements
• (lox-derive) implement OffsetProvider derive macro
• (lox-earth) implement new EOP parser and data provider

Other

• move lox-units code to lox-core
• update SPDX headers and add helper script
• make Lox REUSE-compliant
• get rid of float_eq and lox_math::is_close
• start reimplementation of frame transformations
• refactor all the things
• (lox-time) use provider pattern
• (lox-units/lox-math) move constants to lox-units