Constants (#48)

* Slightly improve error and context handling

* Move default value evaluation to separate function

* Replace tabs by spaces

* Start struct definition implementation

* Start preparation for custom defined types
(#45)

* Implement first working draft of type declarations/definitions (slices not yet supported) (#45)

* Do some renaming (#45)

* Do some renaming (#45)

* Fix type definition base type handling (#45)

* Add tests (#45)

* Revert "Start struct definition implementation"

This reverts commit c81e3c8.

* Fix typo (#45)

* Start constants implementation (#41)

* Use a common function for variable and constant evaluation (evaluateNamedValueDefinition) (#41)

* Improve error message handling

* Add first working draft of single line const definition (#41)

* Fix Const instantiation (#41)

* Define in Expression if it's constant to be able to decide if the assigned value to a constant is actually constant (#41)

* Fix expression evaluation (#41)

* Make sure values are assigned at constant definition (#41)

* Make sure value cannot be assigned to named value if it's a constant (#41)

* Add tests (#41)

* Allow constant and variable definitions via grouping syntax (#41)

* Add simple iota implementation (only simple increment for now) (#41)

* Add tests (#41)

* Update README (#41)

* Update README.md

Author: monstermichl