Added convars to control player maxlevel

smrpg_player_maxlevel controls the maximum level a player can reach
before he won't get any more experience.
smrpg_player_maxlevel_reset specifies if the player should be reset to
level 1 when he surpasses the maxlevel.

smrpg_bot_maxlevel acts the same and a new convar
smrpg_bot_maxlevel_reset was added to give the same power of control as
for the real player maxlevel.
Add auto refresh option to rpgsession menu

Keeps the rpgsession panel updated while it's open