DOPE-226: added array functions, CM extension functions and tests

[martinagallati-ergon]

Info for ARRAY_PREPEND: In the documentation for the function, the values precede the array expression. To implement the variable number of arguments I used vararg, which would impose a need to use a named argument for array. For usability's sake I did it analogous to ARRAY_APPEND(array, vararg values), so a DOPE user does not need to name the array argument.

[m0ne]

In general, there are a few files that exceed the optimal length, none that exceed the maximum, but I would advise against longer lines than necessary. I would go through the PR again and break up long lines. Also, I noticed that the spacing between functions is now mixed (sometimes there is a blank line, sometimes there is none), check that again.

And naming wise, there are places where we use

firstArray: TypeExpression<ArrayType>,
secondArray: TypeExpression<ArrayType>,
vararg arrays: TypeExpression<ArrayType>,

the name arrays is quite vague and it does not seem clear that we mean by arrays firstArray, secondArray, thirdArray, fourthArray,...