UserManual: Add disclaimer as to what GitX is

Add a disclaimer about the intended use of GitX. A lot of people seem to
think GitX is a way to make using a complex system easy. Other think
that they can learn git by clicking their way around GitX.

Signed-off-by: Johannes Gilger <[email protected]>

Author: heipei

Site/UserManual/text/01 - Introduction.markdown

@@ -2,4 +2,15 @@ User Manual
 -----------
 
 This is the GitX user's manual. In this document, you will be able to read
-about everything you need to know on how to use GitX.
+about everything you need to know on how to use GitX.
+
+### Disclaimer
+
+GitX aims to be a graphical wrapper around the most-frequently used
+git-commands, enabling you to satisfy your daily git needs in one consistent
+program. GitX doesn't aspire to be a complete interface for the wide variety of
+git command-line programs with their ever-growing number of options. It's also
+no easy way to learn git. A sound understanding of how git stores data, how it
+works on that data and how to recover from (accidental) deletion of branches
+and commits will not only help you with git but will also enable you to learn
+GitX with greater confidence and speed.