fixed boolean getters recognition, improved performance

[raipc]

By convention, accessors to boolean fields are generated with is prefix. If getter with get method is not found, try to find one with is prefix.

Some performance fix was made with assumption that most getters and setters have public visibility. In this case it is faster to call Class.getMethod method which searches for method defined in parent classes and works about 30 per cent faster (see the benchmark).
If number of methods defined in target class is small, it may be faster to call Class.getDeclaredMethods() and check method name and arguments (but I didn't implement this algorithm)