Add STRING concatenation and Length() function (#107)

* docs: Update README

fixes #94

* docs: update LICENSE year

fixes #98

* refactor: add nullabe to Oberon0.System

* style: Remove empty statement

* feat: enable tool generation

fixes #96

* ci: remove non-existing file from solution

* ci: remove old sonar settings

* feat: implement `Length()`function for type `STRING`

Fixes #103

* build: add sonarqube cloud connection and fixup project settings

* style: fix SQ code smells

* style: add comment for `RemoveFunction`

* test: add exception test for StandardFunctionRepository.RemoveFunction

* refactor: update internal function resolver for testing

* refactor: move internal functions in compiler to separate namespace

* fix: add internal solver optimization for ToString(int, real, bool)

* feat: STRING concatenation

fixes #106

---------

Co-authored-by: Stephen Reindl <[email protected]>

.sonarlint/oberon0.json

@@ -0,0 +1,4 @@
+{
+  "SonarCloudOrganization": "steven-r-github",
+  "ProjectKey": "steven-r_Oberon0Compiler"
+}