grc: Reloading blocks forces reload for all open flow graphs.
grc: Reload marks page as modified only if an error occured during import (i.e. ports no longer exist)
grc: adding version information to flowgraph files using XML processing instructions
grc: moving xml pi into nested data
grc: only fix old message connections if both ends are valid
grc: Generator warning for flowgraphs with a throttle and an external source/sink

The Generator will now issue a warning that it is usually wrong to use
any hardware flow control and a throttle block at the same time.
grc: added save_reports action.
grc: Small fixes to make menu items consistent.
grc: clean-up toolbar
Merge remote-tracking branch 'gnuradio-wg-grc/maint_grcwg' into maint
Merge branch 'maint'
Merge remote-tracking branch 'gnuradio-wg-grc/master_grcwg'