[RigoDaemon] fix xml indentation
[RigoDaemon] extend updates_available() signal with "One Click Update" information
[kswitch] add new method KernelSwitcher.running_kernel_package()

This public method can be used to determine the currently running
kernel package, if it comes from Entropy repositories.
[kswitch] fix _guess_kernel_package_file subdirs generation
[RigoDaemon] add initial One Click Update notification support
[Rigo] debug_rigo.sh: append argv at the end of exec()
[Rigo] add --upgrade cmdline switch
[entropy.fetchers] MultipleUrlFetcher: protect __progress_data with a mutex

Stale information may be used to perform progress calculation.
The mutex ensures that stale data is not used to compute it.
[entropy.fetchers] remove unused variable update_step
[entropy.fetchers] do not calculate any stats until all threads have computed theirs
[RigoDaemon] always avoid transfer_output() signal floods
[RigoDaemon] *UrlFetcher: move class variables inside instance
[entropy.fetchers] make url_path_list and transfer_data protected
[entropy.fetchers] MultipleUrlFetcher: move stats calculation to separate method

_compute_progress_stats can now be used by subclasses to correctly compute
the aggregated statistics without code duplication
[RigoDaemon] fix MultipleUrlFetcher stats computation

Also introduce stale data handling.
[entropy.tools] 1kB is 1000 bytes
[entropy.fetchers] 1kB is 1000 bytes
[entropy.transceivers] 1kB is 1000 bytes
[Rigo] 1kB is 1000 bytes
[entropy.fetchers] do not leak a fd if the abort function raises an exception