add temporary loadout

[nochinator]

Fixes #1363

Changes proposed in this request:

• add new SVAR: playertemploadweap, most instances of playerloadweap now use playertemploadweap, some specificly don't (such as the reset button)
• the reset button has been renamed to "Undo Changes" for clarity
• when playerloadweap changes it also sets playertemploadweap to the same value
• playertemploadweap now also can be updated without affecting playerloadweap, with a button on the loadout menu to do so.

[qreeves]

You don't need to have engine code for this. You can make a persistent string variable with: defsvarp name value

[nochinator]

should clarify the last commit name, undid changes to client.cpp, nothing else

[nochinator]

after further testing it seems like persistent variables made with defsvarp is not avalible in the normal way you get an svar ($varname), doing so throws an error in the console that the variable names alias can't be found. after looking at how other scritps get an svar made in this way it seems like it this is the correct way to get such a variable. it also appears that I am defining it correctly. defining it before the usage does not change anything. could someone check my usage?