[Android][Reflection Layer] Use instance type for Class with instance in XWalkAPI

If a class declares instance in its XWalkAPI annotation, use that class's
bridge type in other classes' bridge call.
Add option to turn on reflection in generator
[Android][Reflection] Use real reflection between wrapper and bridge

Previously, the invoking between wrapper bridge is still directly
funtion call. This commit turns them into real reflection.

Including following parts:
1. Method call will use bridge/wrapper object to get Class and then
get method to invoke. The methods for all exposed API will be get
at instance creation time to avoid getting method object for each call.
2. Static method has no instance to get Class, it has to use class
name to get Class. So it will try to load method for each call.
3. Constructor is complicated, for each class which is not interface,
will register all their constructors' parameter list to ReflectionHelper
in static area. When ReflectionHelper got initialized with specified
ClassLoader, will try to load all registered constructor. Each constructor
will be assigned a unique string to use.