pothos-gui: block properties immediate and time-delay eval

Use immediate eval for different types of entry widgets.
pothos-gui: graph block changes cause scene redraw
pothos-gui: time trigger and limit message window events
pothos-gui: graph block setter checks before marking changed
pothos-gui: only re-query ports after good eval, cleanup GraphBlock
pothos-gui: remove eval errors from report to logger

The errors will only be reported into the block,
and consumers of that block like properties panel,
and future error report generator

This also solves the problem of repeated prints from error'd blocks being re-evaluated
pothos-gui: use toMarkup and darker color for multi-dimensions
pothos-gui: added type eval info tab to properties panel
pothos-gui: recheck endpoints after re-eval and delete connection
pothos-gui: block properties edit widgets are now extensible

Arbitrary property edit widget factories can be registered into the plugin tree.
They are fetched at runtime using the widget type specified in the block description.
pothos-gui: fix to only set property value when changed
pothos-gui: edit widget set style on internal combo box view
pothos-gui: host info tab, protect against null JSON obj
pothos-gui: enable syslog forwarding on the server
pothos-gui: keep log dropping in channel