uhd: added a usrp PC sync option
uhd: added getters for bandwidth setting and range
filter: added fractional_resampler as a renamed fractional_interpolator.

GRC block tree only references this new block and not the interpolator any longer.
blocks: fix file meta data source to handle repeat of files.
Merge branch 'maint'
runtime: changed remove_item_tag to only mark tags as deleted
Merge remote-tracking branch 'jblum/uhd_work'