CMake: build AvTranscoder

* Same problem with scons about the java binding : need to generate the
java files, reconfigure, and build again to generate class files and the
jar. Need to find a solution to skip the reconfigure...
* Useful flags to configure using CMake:
     * CMAKE_BUILD_TYPE: Release / Debug
     * CMAKE_INSTALL_PREFIX: /path/to/install
     * FFMPEG_INCLUDE_DIR
     * FFMPEG_LIBRARY_DIR
* Name of output librairies:
     * avtranscoder.a
     * avtranscoder.so (link + .so with version)
     * avtranscoder-py.so (without link)
     * avtranscoder-java.so (without link)
CMake: build cpp apps

* Add a CMakeList.txt for each app.
CMake: fix install of libraries

Do not need to reconfigure the make file to be able to install
libraries.
CMake: fix java binding

* Do not need to reconfigure the make file to be able to generate class
files and jar file.
* The solution was to add a custom command as a post build of the java
binding which generate java files.