Multilinestring requires double-quote

Multiline strings (Heredoc) now requires double-quote <">. Single-line
strings follow pascal-standard using single-quote.

Better error handling when strings are missing ending quotes.
The ‘+=’ operator supports dynamic arrays

A little syntax sugar for dynarrays which can be used to append new
items to a dynamic array.
Syntax sugar: operator "IN" now support strings

A bit more syntax sugar to simplefy our lifes. The `in` operator can now
be used to check for existence of a substring in a string. Returning a
boolean telling if it exists or not.
> `'world' in 'hello world'`
Merge pull request #8 from WarPie/fixes

HereDoc string, "+=" for dynarray, "In" support for strings.