Added, Find & Replace mode, UDMF: added Linedef activation flags to the "Find...

Added, Find & Replace mode, UDMF: added Linedef activation flags to the "Find Linedef flags" search mode flags list.
Changed, Sound Propagation mode: all sound zones are now shown when no sector is highlighted.
Changed, Sound Environments mode: the mode is now available only in UDMF map format.
Changed, Color Picker plugin: the plugin functionality is no longer available in Doom map format.
Restored the ability to create superimposed lines by dragging them with "Snap to Geometry" mode disabled.
Fixed, Sound Propagation mode: fixed a crash when a single-sided linedef had "Block Sound" flag.
Fixed, Find & Replace mode: in some cases "Find Sector/Sidedef/Linedef/Thing flags" search modes failed to find map elements with required flags.
Fixed, Edit Selection mode: in some cases incorrect geometry was created after applying multipart sector edit when "Replace with Dragged Geometry" mode was enabled.
Fixed a crash caused by eventual GDI font objects overflow.