To make lvl 10 updates always useful, increase barbarian soldier stats

[SirVer]

As discussed in this post:
https://wl.widelands.org/forum/topic/2822/?page=3#post-19596

It will be more viable to get the lvl 10 update always if the following changes are made:

- Em + A: each attack level should increase by +1.2 points
- Barbarian Helmet should boost health by +2 points.

Note that Widelands uses a multiplier internally, e.g. empire soldiers start with 13000 health + 2100 for each level right now.

[GunChleoc (gunchleoc)]

Fixed in build20-rc1