Extend runtime environment with necessary core primitives

The runtime environment needs a proper set of primitives for converting, processing and handling cherry's datatypes. The following functions should be available:

Arithmetic:

• or
• and
• not
• • (Addition)
• • (Subtraction)
• • (Multiplication)
• / (Division)
• mod (Modulo)
• rem (Remainder)
• = (arithmetic equal)
• equal? (structure equal)

Lists:

• list?
• list->string
• length
• cons
• head
• tail
• get
• sublist
• reverse
• range
• append
• filter
• map

Strings:

• string?
• string-eq?
• string->list
• string->symbol
• string->fixnum
• string->float
• string-length
• substring