Added pagination style "infinite"

- Added the ability to use fetchers that do not implement a count() method. The property "paginationStyle" as suggested in #120 must be set to "infinite" to allow fetchers without
a count method.

- Added the option "infinitePageSize" to control the amount of data that should be retrieved an each scroll event. If undefined defaults to the amount of rows that fit into one viewPort page

- Modified some checks, so the fetchers without count methods can work without having placeholders in the table
Since these three lines are exactly the same for both the infinite pagination and the callback in the fetcher.count(), I think they should be unified in the same function. ie:

```
var postCount = function () {
	// Updating the row count here will ensure the scrollbar is rendered the right size
 	updateRowCount();
 
 	// Now that we have placeholders and/or the right row count - update the viewport with blanks
 	self.collection.refresh();
 
 	// Now go and fetch the real items
 	callback();
};

if (self.options.paginationStyle === "infinite") {
	postCount();
} else {
	self.fetcher.count(options, function (result) {
		.... Lines 7506 to 7528 ...
		postCount();
	});
}
```