Multiple improvements / bug fixes to player_weapons_update2 branch

[KirillMysnik]

Resolved confusion between clip/secondary_fire_clip attributes defined in data files and get_clip/set_clip/... methods in _entity/__init__.py
Special thanks to @Mahi for consulting this PR

[KirillMysnik]

Or, as I have seen somewhere in SP, we can keep data file untouched and instead go with something like this

clip = self.__getattr__('clip')
return clip if clip != -1 else 0

Also see issue #137

[KirillMysnik]

Also committed this - not sure how to do a separate PR

[KirillMysnik]

Okay, tried to do a separate PR and successfully failed.

Anyways, as me and @Ayuto discovered, CS:GO's ammo property is ushort, not int, thus simple player.get_ammo was raising exceptions on master. But as Ayuto said, that's not an issue for CS:GO, because it uses primary_ammo_count, weapon-related property (instead of player-related ammo property) which was already implemented in player_weapons_update2 branch.
What we both forgot is this:

if 'grenade' in weapon_manager[self.classname].tags:
    return super(Weapon, self).get_ammo()

and this:

if 'grenade' in weapon_manager[self.classname].tags:
    super(Weapon, self).set_ammo(value)
    return

As you can see, in case of CS:GO, grenades still use the old get_ammo/set_ammo which in turn utilize wrong property type. So I replaced super() calls with the improved code of original get_ammo/set_ammo.

[KirillMysnik]

To anyone who would be handling this PR, please give me directions for fixing #137 - I might just as well include the fix in this PR. I'm not sure if I should go with the solution I proposed in #137 itself, or to only apply the solution in weapons/_entity/csgo/__init__.py, making it specific for CS:GO

[Ayuto]

Thank you!