Explicit coercion and a few other minor changes

[prakashk]

Changes in addition to the coercion related stuff:

• Handle comment lines
• Fixed the parser to accept a terminating semicolon following the last statement in a series of statements.
• Print parse errors when processing code from file or passed with -e option. Assume reasonable defaults for all REPL options.

[stevan]

@prakashk you forgot the MoeContext file actually, however I got it from your initial context branch and I have commited it and pushed

[prakashk]

Ah, I might have missed it when I moved things over to a new branch. Thanks, Stevan.