fix(google-maps): Adds some functions of BaseClass

[guillenotfound]

References: #819

Missing functions yet:

• removeEventListener()
• off()
• trigger()

[ihadeed]

Thanks. I'll merge this for now for the sake of covering all the plugin's functionality. But in the future it would be nice to have a base class that all the other classes extend. I still need to do some experimenting to see how this would work with the decorators we have.

[hartherbert]

Does anyone have interest in implementing the missing functions of the BaseClass?

removeEventListener()
off()
trigger()