Doc: Add intro to accounting

Here's en e-mail I received:

I am a software trainer, training corporate employees in Python, Perl, Unix, GNU make etc. Since 2 days I am trying to understand moneyguru and due to other priorities have kept it aside from today. Today my class was in lazy mood after lunch so I just asked them to evaluate moneyguru and buddi. All of the 40 participants are around 21-22 years old with a bachleor or master degree in IT knowing C, C++, Java and learning python. No one had any experience with any kind of accounting. I was just curious how they will react to learning a entirely new kind of software.

1. at end of 3-4 hours none of the participants were comfortable with moneyguru and just 5 of them were using buddhi decently.
2. all 40 agreed that lookwise MG is better than buddi
3. 30 of them found buddi easier than MG, the remaining 10 had no comments
4. 33 of them felt that the docs of MG were not clear enough, 7 had no comments
5. all 40 felt that the old screencast are better than new one
6. none of them felt that they cannot trust MG to manage their finances because of some crashes, 6 said they will give buddi a try, 15 were happy with MS-Excel, 4 preferred tomboy notes and the remaining didn't care about finance management or said they will put it on paper.

Please take it as positive feedback - because I really like MG. Though I am back to my friendly OOCalc, I will definitely give MG a try in future. But before that I might just try moneydance which also looks promising.

moneyGuru is not more complex than other finance apps (and I think in many regards simpler), but one has to grasp basics of double entry accounting. An intro to accounting in the documentation would help.