Support inclusion or aggregation of other XML files

[v-lopez]

The use case is simple, if I create a BehaviorTree that implements a funcionality in an xml, I'd like to be able to include it from multiple XML's without having to duplicate it.

[facontidavide]

[facontidavide]

Ok, I implemented the feature in a new branch. Once you give me some feedback I will merge it into master.

https://github.com/BehaviorTree/BehaviorTree.CPP/tree/include_xml

To see it in action, execute bin/t07_include_trees passing as first argument either the absolute or relative path to examples/test_files/subtree_test.xml.

Cheers

[v-lopez]

Looks great.

ROS users could probably implement on their own application, some sort of preprocessing of the xml to expand paths relative to a package, ie expand <ros_include pkg="other_pkg" path="subtrees/Talk.xml" /> into <include path="/absolute_path_to_other_pkg/subtrees/Talk.xml" />

[facontidavide]

Indeed. As usual, I prefer to focus on platform independent features first and ROS specific ones later.

[facontidavide]

Please take a look at db72762

I haven't tested it through yet, but it should work.

[v-lopez]

I tested it modifying your example with:
<include ros_pkg="pal_statistics" path="foo.xml" />

And it worked like a charm!

[facontidavide]

Nice!!!