fix(package.xml): upgrade to version 3

to allow for new features like conditional depends accoring to rep [0149].
We use this to differentiate between dependencies required on robots and in
the simulation.

[149]: https://www.ros.org/reps/rep-0149.html

bitbots_localization/package.xml

@@ -1,4 +1,5 @@
-<?xml version='1.0' encoding='utf-8'?>
+<?xml version="1.0"?>
+<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
 <package format="3">
   <name>bitbots_localization</name>
   <version>0.4.1</version>

bitbots_localization_handler/package.xml

@@ -1,5 +1,6 @@
-<?xml version='1.0' encoding='utf-8'?>
-<package format="2">
+<?xml version="1.0"?>
+<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
+<package format="3">
   <name>bitbots_localization_handler</name>
   <version>1.0.0</version>
   <description>The bitbots_localization_handler uses high level information to improve 

bitbots_visual_compass/package.xml

@@ -1,4 +1,6 @@
-<package format="2">
+<?xml version="1.0"?>
+<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
+<package format="3">
   <name>bitbots_visual_compass</name>
   <version>0.1.0</version>
   <description>The visual_compass package</description>