roslaunch: add systemd unit files (resolves #224)

various minor improvements 

ar-track-alvar: initial commit

log4cxx: keeping in-source build (resolves #252)

This commit provides the autotools-brokensep class and uses it for
the log4cxx recipe.
The autotools-brokensep indicates that the log4cxx currently cannot
handle out-of-source builds, and hence the in-source build must be
kept until this is resolved.
The autotools-brokensep class is a copy of the autotools-brokensep
class provided in the openembedded-core commit 006b8a78 [1].
To make this commit backwards compatible to even earlier versions
of openembedded-core, we provide this class in meta-ros ourselves.

[1] http://cgit.openembedded.org/openembedded-core/commit/?id=006b8a7808a58713af16c326dc37d07765334b12

amcl: adjusting license string (resolves #250)

Updates till early May 2014

The version 1.8.5 incorporates the local patch, and hence the local
patch is removed. Furthermore, it now requires roslint.

roslint is needed for the latest version of xacro.

improving README.md

A number of new recipes

libfreenect: updating to 0.2.1 (resolves #248)

Updating to 0.2.1, and correcting shipping of fakenect libraries.

In the commit 21f7799e, I manually
modified the patch, but it slipped my eyes to adjust the line
information in the patch accordingly.
This commit corrects the line information, so that the patch can
now be applied correctly.