Add more information to MissingMandatoryField exception

[BlobbyBob]

Issue

When getting a MissingMandatoryField exception it can be hard to identify from which Telegram Method it came, since the stack trace only shows the TelegramMethods class as source.

Suggestion:

Change the error message format to:
'The field "%s" in ' . get_class($this) . ' is mandatory and empty, please correct' (Abstracts/TelegramMethods.php, l. 78)

[unreal4u]

Good suggestion!

Will include the change, however I will be kind of busy this weekend, so I think I will pick this up on Monday 25th.

Greetings.