digital: made the demod examples clearer
grc: Fixed Bug #485 by gracefully exiting when user sets GR_DONT_LOAD_PREFS=1 GRC_BLOCKS_PATH=
core: added operator == for tags
core: added remove_tag_item()
Merge remote-tracking branch 'mbant/demod_examples'
Merge remote-tracking branch 'mbant/fix485'
Merge remote-tracking branch 'mbant/equal_for_tags'
Merge branch 'master' into next

Conflicts:
	gr-digital/examples/demod/ber_simulation.grc
	gr-digital/examples/demod/digital_freq_lock.grc
	gr-digital/examples/demod/pam_sync.grc
	gr-digital/examples/demod/pam_timing.grc
digital: fixed up examples for the updated location of blocks.
digital: fixed a typo preventing timing loop update in GRC.
digital: setting grid position of sliders in digital examples.