merging "long" and "int" datatypes

[julochrobak]

Bandicoot currently supports three numeric data types (int, long, real) - http://bandilab.org/specification.html#primitive_types

Two different data types for signed integers together with strictly explicit type conversions introduces some overhead and complexity when writing expressions and using functions such as Time.Now or String.Index.

For example, the following code requires explicit type conversions to work

type TimeWindow {
    start long,    # start of the window as a unix timestamp
    duration int  # duration in seconds
}

fn InPast(in TimeWindow) TimeWindow {
    return select (Time.Now > start + (long duration)) in;
}

This issue suggests to remove the "long" data type and leave only 64-bit version of "int" data type.