Add single and multiple marker board detection nodes

[naiveHobo]

• Adds single_board and multi_board nodes to detect aruco marker boards
• Publishes the same topics and msgs as single and double nodes
• Adds sample launch files to launch single and multi board setups
• Adds sample yaml files for single and multi aruco marker boards

closes #5

[lwohlhart]

Looks like a valuable feature add-on;
any specific reason why it's not pulled ?

[v-lopez]

No, just lack of time on my side.

But a reminder, that melodic has it's own branch using a newer version of the Aruco library.