Add method to world class to allow for more elegant config changes

[jrenaud90]

Currently, to change a configuration on a planet you need to A). know a potentially complex series of configuration keys and B). make a separate call to the planet's reinit(). For example to change the rheology of the earth's lower mantle:
earth.config['layers']['Lower_Mantle']['rheology']['compliance_model'] = 'Andrade'
earth.reinit()

All of those keys are case sensitive and any mistake will cause a crash due to KeyError. This can be confusing for someone new to TidalPy.

It would be nice to have a method that:

• Reduces the number of keys needed (by making some assumptions/guess about what the user really wants to change.
• Cleans up the remaining keys so that if the user did/didn't capitalize something it doesn't cause a crash.
• Allows the user to change multiple configs with one method call.
• Automatically calls reinit once all the configs have been changed (user togglable).