proxy: Enable DBus property extraction via CLR properties

Properties were previously involved in some name mangling to separate
them from normal methods, events were dealt with in a similar way. As
result, although signals worked correctly, properties did not.

This patch flips the implementation process on its head, first building
a set of methods for evaluation and removing pairs as properties or
signals (events) are implemented before passing the remainder to the
general function.

Property Get/Set is handled by two additional functions in the BusObject
class, the IL is generated specifically for them. Event listener
addition and removal IL generation is refactored into its own function
in the same way.