Finish parser

[jbrezmorf]

• finish Array class to represent array structure of the scalar expressions

  • [x] elementwise operations
  • [x] mat mult
  • [x] indexing, splicing
  • [x] broadcasting, composing
  • [ ] user API

• [x] basic spirit grammar

• [x] AST

• [x] conversion of AST to processor

• [x] chained relational operators

• [x] grammar rules for: indexing, variadic functions, composing, mat mult

• [x] translate variadic functions and mat mult to array operations

• [x] speed tests

• [ ] safe ScalarNode

• [x] default workspace for variables

• [x] CMake

• [x] update Readme

[jbrezmorf]

Mostly dome, safe ScalarNod not necessary as long as it is an internal code.