Update license (#125)

Change the license identifier in package.xml to conform to SPDX, add a license text file, and install
the license text file in accordance with the terms of the BSD 3-clause license.

CMakeLists.txt

@@ -19,6 +19,10 @@ install(DIRECTORY launch/
    FILES_MATCHING PATTERN "*.launch"
 )
 
+install(FILES LICENSE.txt
+   DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION}
+)
+
 if (CATKIN_ENABLE_TESTING)
   find_package(roslint)
   roslint_python()

LICENSE.txt

@@ -0,0 +1,29 @@
+BSD 3-Clause License
+
+Copyright (c) 2013-2021, ROS Device Driver Contributors
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its
+   contributors may be used to endorse or promote products derived from
+   this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package.xml

@@ -9,7 +9,7 @@
 
   <maintainer email="[email protected]">Ed Venator</maintainer>
 
-  <license>BSD</license>
+  <license>BSD-3-Clause</license>
 
   <url type="website">http://ros.org/wiki/nmea_navsat_driver</url>