[TIMOB-27874] TiAPI: Add Ti.Locale.parseDecimal() method

*Summary:* Titanium has APIs to turn numbers into localized strings, but there are no APIs to convert a localized numeric string back to a number type. *Proposed Solution:* Add the following method. Ti.Locale.parseDecimal(text \[, locale \]); // Returns number type. If the above was given an invalid string, then it will return NaN (Not-a-Number), which matches JavaScript's standard Number.parseFloat() method behavior. *Main Use-Case:* A TextField using a decimal keyboard type will be using the device's current locale for the decimal separator. This means the decimal separator will be a comma , in Europe. It will can also be a unicode decimal separator for Arabic locales. When reading the TextField string "value" property, the app developer will need an easy means of parsing the localized numeric string back to a JS number type. *Test Cases:* Converting a number to localized string and then back to a number.

var oldNumericValue = 123.456;
var stringValue = String.formatDecimal(oldNumericValue);
var newNumericValue = Ti.Locale.parseDecimal(stringValue);
if (Math.abs(newNumericValue - oldNumericValue) < Number.EPSILON) {
 	console.log('Parsed number matches original number.');
}

Parsing equivalent numbers from 2 different locales.

var number1 = Ti.Locale.parseDecimal('1,234,567.8', 'en-US');
var number2 = Ti.Locale.parseDecimal('1.234.567,8', 'de-DE');
if (Math.abs(number1 - number2) < Number.EPSILON) {
	console.log('Parsed numbers match.');
}

Strings that cannot be converted to a number will return NaN.

var result = Ti.Locale.parseDecimal('Invalid');
if (Number.isNaN(result)) {
	console.log('Invalid string returned NaN.');
}