merged new features from hydro-devel
fixed handling of numerical values in xacro:if and xacro:unless

string value from eval_text() was not converted to numerical value before comparison to 0/1
simplified extension handling, direct calling eval_extension
recursively evaluate properties
Merge remote-tracking branch 'ubi-agni/groovy-devel' into groovy-devel
backported indigo-devel fixes for recursive_eveluation and tests