urdfdom-headers: Allow empty package to be created

Bitbake gives a dependency error when IMAGE_FEATURES += " dev-pkgs" is set.

This is because the urdfdom-headers package contains headers only, as a
result bitbake packages them into urdfdom-headers-dev and leaves
urdfdom-headers empty.

Since there are no files to be packaged into urdfdom-headers bitbake
doesn't create the package. urdfdom-headers is a dependency
of urdfdom-headers-dev by default so bitbake errors when building an image
with dev-pkgs enabled.

ALLOW_EMPTY tells bitbake to create a package even when nothing is in it.
This resolves the dependency issue of urdfdom-headers-dev
http://www.embeddedlinux.org.cn/OEManual/recipes_packages.html

adjust some LIC_FILES_CHKSUM retroactively to version update

Many recipe updates to current version of indigo release

While testing the version updates, I noticed that the
camera-calibration-parsers were missing the roscpp dependencies,
and hence do_configure failed with:

```
|   Could not find a package configuration file provided by "roscpp" with any
|   of the following names:
|
|     roscppConfig.cmake
|     roscpp-config.cmake
|
|   Add the installation prefix of "roscpp" to CMAKE_PREFIX_PATH or set
|   "roscpp_DIR" to a directory containing one of the above files.  If "roscpp"
|   provides a separate development package or SDK, be sure it has been
|   installed.
| Call Stack (most recent call first):
|   CMakeLists.txt:4 (find_package)
|
|
| -- Configuring incomplete, errors occurred!
```

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