Add support for automatically checking updates

Automatically checking updates is an important feature and have been allplied to many softwares. As for UGENE, nowerdays it is developing quickly and users should benefit from such updates. However, now it only supports checking updates manually and thus many users would lose updates frquently. Even for some Linux distributions, the official package is very old. (In Ubuntu 10.04 LTS the UGENE remains 1.5)

Thus I suggest to add support for checking updates automatically, just like Oracle VirtualBox(only check updates, not apply updates). When a user install and run UGENE for the first time, a message box should appear to let user choose whether checking updates automatically or manually. Such setting should also be able to configured in the "Preference" menus.