Breaking braces refactor

[jkrumbiegel]

• Breaking: The $() interpolation syntax is replaced by {} for single columns (or broadcasted multi-columns)
• Added {{}} for referring to multiple columns as a tuple.
• Breaking: No more flag macros, replaced by explit @byrow, @bycol, @passmissing, @astable.
• Breaking: All(), Between() and Not() have to be interpolated with {} and can't be used standalone anymore.