Eternity Engine configuration: moved portal related sector flags to the portals tab of the sector edit form

Sectors Mode: fixed a crash when merging sectors while a shared linedef between them was shown as an association

Fixed a bug where saving WADs that didn't have their data starting right after the header would corrupt the file. Fixes #531

Map Analysis Mode: fixed a crash when the sidedef of 1-sided lines had upper/lower textures defined. Fixes #533

Using the "Reset plane slope" action now sets the floor or ceiling heights to the height of the plane at the sector's bounding box center

Fixed a bug where resetting the ceiling slope in the UDMF sector edit form would invert its original height

Error Checker: added config options to ignore unknown textures on sidedefs for certain actions. Resolves #518

Find and Replace Mode: fixed a bug where searching for linedef or thing action and arguments would not show "0" as an argument if it was the last arguments. Fixes 528

DECALDEF parser: fixed a problem where opening curly braces in the same line as a decal definition caused a parsing error

Decorate/Zscript Actors that replace other actors should now display the correct actor name given through the $Title editor key. Fixes #122

Added option for special handling of triangular sectors when doing visual sloping. When enabled it'll always select an opposite smart pivot handle. Enabled by default, can be disabled in Tools -> Preferences -> Editing -> Opposite side/vertex is smart pivot handle on triangular sectors

Fixed a bug where map elements could be selected multiple times when paint selecting in visual mode. Fixes #519. Fixes #520

Some refactoring regarding visual sloping

Fixed a problem where values specified with the UserDefaultValue editor key in ZScript were not applied for float/double values

Using visual sloping to create a horizontal slope will now remove the slope and set the appropriate sector height instead
The Edit Sector dialog will not remove horizontal slopes anymore unless necessary

Visual Mode: fixed a problem where pasting a texture to a 3D floor sometimes didn't show the pasted texture immediately