Operating ABE

To operate ABE and its functions:

Use abeInit to start an ABE session for a given cellview. ABE functions can only be performed after ABE is initialized.
Create ABE layers as a clean layer or populated with shapes from a cellview.
Hierarchical shapes can be copied from a cellview but are flattened on the ABE layer. Shapes can also be added to an ABE layer using a list of points.
To perform two-layer ABE operations you need two input ABE layers and have the general format:
```
abeLayerOp(
o_abeLayer1 
o_abeLayer2 
o_abeOutputLayer 
) 
=>t / nil
```
One-layer ABE operations require one ABE input layer and have the following general format:
```
abeLayerOp(
o_abeInputLayer 
o_abeOutputLayer 
) 
=>t / nil
```
Save ABE layers to the current ABE session cellview or a Graphics Editor highlight set.
Use abeDone to end an ABE session. This frees up the memory that was used for the session.
Use abeClearLayer to clear an ABE layer. This is helpful to re-use existing ABE layers.
Use abeRemoveLayer to remove an ABE layer. This frees up the memory that was used for the ABE layer and is useful when you are doing a series of operations. For large designs, a significant amount of memory can be used by each ABE operation.