Add tests for AST when constructing by hand
Implement multiselect with array syntax
Pullup common multiselect code into base class
Add multiselect tests for multifieldlist
Remove unneeded pretty_print

The base class implementation is exactly the same.
Merge branch 'array-multiselect' into develop

* array-multiselect:
  Remove unneeded pretty_print
  Add multiselect tests for multifieldlist
  Pullup common multiselect code into base class
  Implement multiselect with array syntax
  Add tests for AST when constructing by hand