implement -repr for most types
implement print, println, pr-str, pr and prn

print does not add a newline anymore, but println does. print also
inserts spaces between arguments now.
fix usages of print

that is, use println and don't add now extraneous spaces.
print values using -repr on the repl
add tests for str and -repr

and add -repr on symbols and fix pixie.test/show
implement -repr for Type
Merge pull request #94 from heyLu/printable

Make things printable