blocks: added a filter (as a tag's key string) to the tag debug block.
digital: set relative_rate in pfb clock sync blocks to correctly move tags.
digital: fixed pfb clock sync to use forecast and not do bookkeeping in work.
digital: adding a correlate and sync block for burst modem detection.
digital: wip: working tag support for phase and timing est. in costas and pfb clock recovery loops.
Merge remote-tracking branch 'trondeau-github/grhack13' into grhack13
filter: made stand-alone arbitrary resampling filter.

Could be worked into pfb_arb_resampler work functions, but is not, yet.
digital: wip: using new arb resampler to manage building of preamble matched filter.
docs: typos fixed.
Merge branch 'grhack13' of https://github.com/trondeau/gnuradio into grhack13
digital: Added QA for correlate_and_sync.