libtinyxml2: update 2.2.0 -> 3.0.0

Also misc recipe cleanup, take license text from tinyxml2.cpp source
file instead of using the entire readme.md, and build using cmake.

Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>