addition operator for ggb object to support ggplot-like syntax
Usage
# S3 method for ggb
+(o1, o2)
Arguments
- o1
the first object inheriting the ggb class
- o2
the second object inheriting the ggb class
Value
a modified version of the o1 object with o2 added to it
Details
Note that the addition operator always clones the underlying o1 object
rather than modifying it in place