Added the ability for plugins to choose the toolbar section in which to add a button
Added beginning of ZDoom USDF conversation editor plugin

Exposed more DECORATE information to plugins and Things now have an Actor property (ActorStructure) when they are loaded from DECORATE
Added two new type handlers that can be used in UDMF ('Thing Type' and 'Thing Class')
Polished the browse icons and browse buttons.
Added more events for plugins to intercept.

Added Copy and Paste object properties for classic modes
Added some options for toolbar customization

@ Modified the BlockMap class with a template for the BlockEntry class and added custom block size (must be a power of 2 greater than 1)
@ Added BlockMapMode as an example to show how the BlockMap class behaves

Fixed resource options dialog being showed outside the screen boundaries on small screen resolutions

- Added floor/ceiling raise/lower by 8 mp actions to Sectors mode
@ Added simple CRC32 calculator class (using Crc32 from sharpziplib)

Fixed some drawing uglyness with thing icons in thing type browser

Added actions (and buttons on toolbar) to flip a selection horizontally or vertically in Edit Selection mode

changed a lot in resources loading, how unknown textures are displayed and how corrupt textures are handled

- fixed crash in Find & Replace Mode when opening the mode for the second time after opening a new map
- added buttons on the toolbar for Find & Replace Mode and Map Analysis Mode
- now allowing direct switching from volatile mode to another volatile mode (old mode is cancelled)

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added a default "All" texture set which always contains all textures and (like the "Others" set) cannot be removed

- fixed curve lines menu item in linedefs menu
- changed the test map drop down menu (nomonsters option is now in the menu instead of a seperate button)

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