main loop uses new flags and common methods in util: db, keymanager set up; passes KeyRing/Session string to gui

- keyring: keyring/session identifier used by key manager
- keystore: choice of db/file key storage
- import message updated
- export: name of directory to export keys to (was bool)

- keyring: keyring/session identifier used by key manager
- keystore: choice of db/file key storage
- import message updated
- export: name of directory to export keys to (was bool)

Conflicts:
	install.sh

- introduce gui.Stop()
- remember state with open
- stopping ethereum stack is not gui concern, moved to main
- stopping mining, gui and ethereum handled via interrupt callbacks
- ^C triggers exactly the same behaviour as quit via menu

- only add the gui logger after window is shown otherwise slider wont be shown
- need to silence gui logger after window closed otherwise logsystem hangs
- gui.GetLogLevelInt() extra function needed to give correcty int typecast value to gui widget that sets initial loglevel to default

fix logSlider: now has 5 levels, initialized to gui.GetLogLevel which is set through command line flag (defaults to InfoLevel)