* Initial version of SharedContacts from data message. Need to change location of avatar downloaded and fix plain text mode
* Made empty strings for json null and fixed plaintext output
* Removed old comments, simplified if-statement and added a 'leadingSpaces' field to the print attachments/mentions functions
* Added AsamK's changes
* Modified the Manager class to provide an ExecuterService for the SignalServiceMessageSender.
* removed unnesessary comment
* Changed the ExecutorService to a unbounded newCachedThreadPool
Co-authored-by: Cutkh <cutkh@users.noreply.github.com>
