Remove "angle" variable

It isn't needed for flags
Change cg_ffaWeaponMode into cg_weaponMode
Make some changes to the weapon mode

- Change cg_weaponMode default value to "select"
- Change g_forceWeaponMode default value to "no"
- Fix "you can't join to the team of the player you're spectating"
- Weapon selector only shows up if it's a team game and the weapon mode (forced or not) is "select"

When g_forceWeaponMode is "no", cg_weaponMode or bot_weaponMode are used to choose the weapon mode.