Allows the SavegameManager to destroy all saves related to the current UUID session so hardcore mods can enforce this safely instead of needing to go nuclear.
Adds a multiplayer tab to allow hosting and joining games from within the GZDoom launcher rather than needed to use the command line. This has its own set of defaults independent from the main play page which necessitated rewriting how this information is passed and stored in the backend. A startup info struct is now passed back which has its defaults set from the cvars and then propagates any changes to it back to the defaults after selection is complete, making it much simpler to interface with the engine defaults.
* it is now possible to switch back to the main intro loop from the fullscreen console.
* do not distort the background of the fullscreen console. Always draw the console on top of what the main loop currently displays with a translucent black overlay.
* do not use the CONPIC for the fullscreen console as it tends to be more of a distraction than an asset when filling the entire screen.
* cleaned up c_console.cpp and moved several pieces of code unrelated to actual console management out of it.
Sensitivity scaling of both axes is now exposed as a raw factor to the user instead of obscuring it behind an unclear 'prescale' boolean.
This also consolidates the coordinate processing code to prevent such discrepancies as were present here from happening again.
Migration code for old config settings is present so that this change does not affect existing configurations.
* removed refreshFreq variable and related code. This only got into the backend because of stupid interpolation code in some of the Build games which has long been removed.
* save FixedBitArrays as base64 in savegames.
* allow indirections in the string table - by prefixing the language string with '$$' the remaining text is interpreted as another string label to resolve.
* constexpr in palette code, also replacing #defines with enums.
