Add 'is' and 'can' prefixes to boolean 'get' methods

Boolean get methods usually start with 'is' or 'can' rather than 'get'.

Now a frame can use more natural method names:
```java
    @Property("boolean")
    public boolean isBooleanPrimitive();
    
    @Property("boolean")
    public boolean isBoolean();
    
    @Property("boolean")
    public boolean canBooleanPrimitive();
    
    @Property("boolean")
    public boolean canBoolean();
```