Modified the README to explain eclipse cdt usage with cmake.

README.txt

@@ -17,7 +17,29 @@ Building using cmake
  - cmake ..
  - make (will build every sketch)
  - make ArduPlane (will build just ArduPlane etc.)
+ 
+Building using eclipse
+-----------------------------------------------
 
+	assuming source located here: /home/name/apm-src
+	You can either download it or grab it from git:
+	git clone https://code.google.com/p/ardupilot-mega/ /home/name/apm-src
+	
+ 	mkdir /home/name/apm-build 
+ 	cd /home/name/apm-build
+ 	cmake -G"Eclipse CDT4 - Unix Makefiles" -D CMAKE_BUILD_TYPE=Debug ../apm-src -D BOARD=mega -D PORT=/dev/ttyUSB0
+ 	
+ 	Note: unix can be substitude for MinGW/ MSYS/ NMake (for windows)
+ 	(see http://www.vtk.org/Wiki/Eclipse_CDT4_Generator)
+
+    Import project using Menu File->Import
+    Select General->Existing projects into workspace:
+    Browse where your build tree is and select the root build tree directory. Keep "Copy projects into workspace" unchecked.
+    You get a fully functional eclipse project
+    
+    You can also import the source repository (/home/name/apm-src) if you want to modify the source/ commit using git.
+    
+  
 Build a package using cpack
 -----------------------------------------------
  - cd build