Help: Add screenshots to "income and upkeep"

data/core/help.cfg

@@ -219,11 +219,15 @@ Units not only cost gold to Recruit or Recall, they also require money to suppor
         title= _ "Income and Upkeep"
         text= _ "In Wesnoth, it is not enough simply to recruit units and fight. You must watch your gold as well, especially in campaigns, where you can carry extra gold over from one scenario to the next. There are two aspects to this; <italic>text='income'</italic> and <italic>text='upkeep'</italic>." + _ "
 
-Income is simple. You have a base income of 2 gold per turn. For every village you control, you gain one additional gold each turn. Thus, if you have ten villages, you would normally gain 12 gold each turn. Your upkeep costs are subtracted from this income, as detailed below." + _ "
+Income is simple. You have a base income of 2 gold per turn. For every village you control, you gain one additional gold each turn. Thus, if you have ten villages, you would normally gain 12 gold each turn. Your upkeep costs are subtracted from this income, as detailed below." + "
+
+<img>src=help/income-upkeep1.png align=middle box=no</img>" + _ "
 
 Upkeep is also fairly simple. Each unit requires an amount of Upkeep equal to its level. You can support as many levels worth of units as you have villages, without paying any upkeep. However, for each level of unit beyond the number of villages you have, you must pay one gold per turn. For example, if you have twelve level one units and ten villages, you would have to pay two gold each turn in upkeep." + _ "
 
-Upkeep costs are subtracted from your income, so in the case of twelve levels of units and ten villages, your resultant Income would be 10 gold per turn." + _ "
+Upkeep costs are subtracted from your income, so in the case of twelve levels of units and ten villages, your resultant Income would be 10 gold per turn." + "
+
+<img>src=help/income-upkeep2.png align=middle box=no</img>" + _ "
 
 In general, the base income, the amount of gold you get per village per turn, and the number of unit levels each village can support are configurable, but in campaigns they are almost always the values described above. The <italic>text='Scenario Settings'</italic> tab of the <italic>text='Status Table'</italic> dialog shows the values for the current scenario." + _ "