Display message after saving/deleting activities

[enriquezrene]

When an existing activity is removed or saved we need to display a message indicating the data has been removed/saved successfully or if an error happens we need to let users know about it. Examples of messages can be:

Successful delete:

The activity has been removed successfully 

Successful save:

The activity has been saved successfully 

Error

An unexpected error happened, please try again later.