HTML Output destroys spaces

[mzijlstra]

Make the output window use PRE

[mzijlstra]

Really, I need to redo the whole I/O sub system:

• Use wr.stringify() (see other issue) for output.
• No longer require that the output expression evaluates to string
• No longer have quotes around input and output
• No longer default to having a new line on print -- instead require \n
• In other words, enable single character printing sequentially building a line

[mzijlstra]

• Used JSON.stringify() instead.
• Removed the requirement that output needs a string
• There are no longer quotes around things in the Input/Output window
• Output does not create a newline by default, input does, and all '\n' are replaced with newline
• One can now sequentially build lines by printing one character at a time