Implement SDK Enhancements

[oxnr]

1. For every callback example in documentation Boolean type parameter is used (new TGRequestCallback() ) although in most cases there should be another type parameter.
2. Create user. Documentation states “Our SDK provides three convenient ways to create users “ but it gives an example of only createAndLoginUser method.
3. Search users. Social ids section provides example with searchWithEmails method.
4. Send events section states “In the first section of the Android Guide you can learn more about configuring the flush settings.” but there is no such information in the fist section.
5. Create post. Documentation fails to describe the process of creation of TGAttachment object. Some information on at least required fields would be nice.
6. There is a call for the static method post() in Documentation, but the actual method is posts().
7. As Documentation describes SDK only in broad strokes and doesn't provide details on many SDK methods and objects it would be nice to have detailed JavaDoc.

SDK ver 1.1.6

1. posts().getPost() method always returns TGPost object with isLiked field set to false. As there is no setter for isLiked field the only way to get an updated post is to retrieve all the posts and parse through.
2. createdAt() is always null for all applicable objects.
3. It would be nice to have separate field in TGUser object for an userpic url.
4. TGAttachment object requires TGCacheObjectType but there is no documentation for which one should be used.
5. Attachment type is string and it isn't clear is it checked server side as Documentation states “An attachments of a post can currently be of type text or a url”.