This commit provides a recipe for a core image to start roscore, and
also tunes the README.

For starting roscore, it requires a number of runtime dependencies.
At the moment, all runtime dependencies, even recursive runtime dependencies,
are added only in the roslaunch recipe. Hence, the recipe contains all
runtime dependencies.
At a later stage, one should move the recursive runtime dependencies into
the appropriate recipes.

In the topic-tools recipe, a QA error was raised as the .debug files were put
into the main package. By adding this line in the catkin class, the files are
now placed in the dbg package.

catkin.bbclass: Stage /usr/etc sysroot direcotry 

The CMake generate_messages function from the genmsg package
detects the installed message generators via files in the
/usr/etc/ros/genmsg directory. Stage the /usr/etc directory
manually as it is not a common path.

Fixed #50

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

The roscpp-core package is a meta-package. This meta-package and the concept
meta-package in general is not used for any purpose in our layer.

Since its initial contribution in f73e30ae,
the topic-tools had an untested md5 hash for the license check.

Minor organisation improvements

CONTENTS: reducing the CONTENTS file to a general description of some files and the basic directories

Minor improvement in message_filters

The recipe contains a hyphen in their name, hence we must use the ROS_BPN
variable.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@oss.bmw-carit.de>

Work on catkin and updating all recipes to improve the aspect of which native packages the packages really depend on. 

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Rostest depends on its own package and therefore needs to search
in the devel space for the rostestConfig.cmake during native
build.

| CMake Error at /.../usr/share/catkin/cmake/find_program_required.cmake:5 (message):
|   rostest not found
|

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

All ROS packages with install tools in the bin directory or install
python code with is used by other packages should be used as native
version. Adapte the DEPENDS accordingly.

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Adapt genmsg to handle msg files relatively to the current
cmake path. Without this modification genmsg failed to generate
messages because it pass a path without sysroot to the python
code.

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Catkin require a .catkin file in all CMAKE_PREFIX_PATH to add them
to the CATKIN_WORKSPACES. Remove this requirement as it couldn't
be satisfy when catkin packages are installed into the common usr
prefix. Without this adaption catkin couldn't find all files.

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

The local version was replaced by a solution from a catkin
maintainer.

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

Replace CXXFLAGS += "-fPIC" with EXTRA_CXXFLAGS to allow native
build and use relative paths to simplify recipe.

Signed-off-by: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>

In the previous commit, I accidently also edited another line than intended and
missed to see the accident before committing.
This commit reverts that accident.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@oss.bmw-carit.de>

This prepares the script to produce directly into the git submodule.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@oss.bmw-carit.de>