Add text read (prompt/input) block about blockly HOT 3 CLOSED

update with type conversion.

language:

Blockly.Language.text_prompt = {
  // Prompt statement.
  category: 'Text',
  helpUrl: 'http://www.liv.ac.uk/HPC/HTMLF90Course/HTMLF90CourseNotesnode92.html',
  init: function() {
    this.setColour(160);
    this.appendTitle('read');
    var menu = new Blockly.FieldDropdown(this.OPERATORS);
    this.appendTitle(menu, 'TYPE');
    this.appendInput('', Blockly.INPUT_VALUE, 'TEXT');
    this.setOutput(true);
    this.setTooltip('Prompt for user input with the specified text.');
  }
};

Blockly.Language.text_prompt.OPERATORS =
    [['string', 'STRING'], ['integer', 'INTEGER']];


python generator:

Blockly.Python.text_prompt = function() {
  // prompt a user input dialog.
  var mode = this.getTitleValue('TYPE');
  console.log(mode);
  var operator = Blockly.Python.text_prompt.OPERATORS[mode];
  var argument0 = Blockly.Python.valueToCode(this, 'TEXT', true) || '\'\'';
  return operator+'(raw_input(' + argument0 + '));\n';
};

Blockly.Python.text_prompt.OPERATORS = {
  STRING: 'str',
  INTEGER: 'int'
};

Issue 29 has been merged into this issue.

Done in r260 and r261.

Modal I/O is a terrible UI experience.  As such, Print and Prompt should be 
treated as emergency functions.  Any real environment would have much better 
I/O APIs.  But they are still very useful for debugging and "Hello World" 
applications.

Since this is an emergency debugging function, I've converted the prompt 
message input into an inline field.  This is simpler and sufficient most of the 
time.  If one really wants a dynamically customizable message field, then one 
should probably be using a better API.

Type conversion functions are also something we need, but I've folded them into 
this block, again for convenience.

The use of window.prompt in Dart is questionable.  It will only work in a 
browser, not in the command-line version.  Likewise there's a complicated 
asynchronous readLine version that only works in the command-line version and 
not the browser.