pothos-library: simplify the topology commit async actions
pothos-blocks: network endpoint open/close requires buffer

The buffer cannot be non-empty, we need to be able to drain
data from runtime to be able to perform the handshake.
Size zero buffers will never drain the partial packets.
So the handshake gets stuck...
pothos-blocks: network endpoint use chrono, lower def timeout
pothos-library: use PROJECT_SOURCE_DIR in Doxygen build
pothos: disable unused poco libraries to simplify build
pothos: added top level install target
pothos-widgets: work on 2d planar select widget
pothos-widgets: working plane selection implementation
pothos-widgets: planar select docs and display tweaks
pothos-widgets: added click select, moved pos math
Merge branch 'planar_select'
Merge branch 'master' into periodigram_work
pothos-widgets: added averaging factor to the periodigram