various BitcoinKit fixes

- restored stack trace info for Java exceptions
- fixed sync progress calculation
- clear transactions list before rebuilding blockchain (#132)
- don't ignore incoming and already confirmed tx (fixes #193)
- track changes to pending transactions after restart (fixes #192)
fixed refresh delay when confirming transaction

the refresh wasn't done on the main thread, which caused a several
seconds delay and a warning about core animation threading problem
(fixes #151)