emuscv: correct the core's documentation page

[MaaaX-EPOCH84]

I am the author of the EmuSCV core. The page carried five factual errors, one of which tells users a working feature does not work.

States were marked unsupported. Save states work, and so do rewind and fast forward. This is the one that matters: users were told to expect nothing.
Sample rate read 48000/00 Hz. The core runs at 44100.
Base width and height were given as 960x720, which no setting produces. The frame buffer depends on the RESOLUTION and DISPLAY options; the six real sizes are listed instead.
Three core options were documented out of ten, and the description attached to CONSOLE ("forced sleep in main thread for lower CPU use") came from another core. All ten are now described.
One BIOS filename was missing from the list of six the core accepts, upd7801.s01.
The Not Finished marker is dropped, and the .cart format is explained, since users otherwise wonder why a new file appears in their save directory after every launch.