Improve Lisp

[vinc]

• Add println function
• Add args variable containing the list of arguments the script was called with
• Add or and and boolean operations
• Add cat and join string operations
• Add system command to execute programs

[vinc]

Boolean operations:

> lisp
MOROS Lisp v0.2.0

> (and true false)
false

> (or true false)
true

[vinc]

Argument parsing:

> lisp /tmp/lisp/factorial.lsp 20
2432902008176640000

> lisp /tmp/lisp/fibonacci.lsp 20
6765

[vinc]

Before last commit:

> [time lisp /tmp/lisp/factorial.lsp 300
inf
Executed 'lisp /tmp/lisp/factorial.lsp 300' in 0.233964s

After:

> time lisp /tmp/lisp/factorial.lsp 300
inf
Executed 'lisp /tmp/lisp/factorial.lsp 300' in 2.308953s

[vinc]

> time lisp /tmp/lisp/factorial.lsp 300
inf
Executed 'lisp /tmp/lisp/factorial.lsp 300' in 1.857022s

[vinc]

> time lisp /tmp/lisp/factorial.lsp 300
inf
Executed 'lisp /tmp/lisp/factorial.lsp 300' in 1.214967s

[vinc]

> time lisp /tmp/lisp/factorial.lsp 300
inf
Executed 'lisp /tmp/lisp/factorial.lsp 300' in 0.585063s

[vinc]

Before previous commit:

> time lisp /tmp/lisp/factorial.lsp 1000
inf
Executed 'lisp /tmp/lisp/factorial.lsp 1000' in 12.995001s

After:

> time lisp /tmp/lisp/factorial.lsp 1000
inf
Executed 'lisp /tmp/lisp/factorial.lsp 1000' in 3.843024s

And now are back to the performance we had before we replaced both Env and its reference to its parent env &'a Env with Rc<RefCell<Env>> that will allow us to do TCO by changing the recursive calls to eval with a loop. We couldn't do that before because of the difference in lifetime.