Enhance entries modal

[enriquezrene]

We need to add a few constraints in the existing modal used to work with entries:

1. Make the project required
2. Make the activity required
3. Make start/end date/time required

Mark the button Save as disabled if the above-mentioned validations fail.

We need to display a message indicating the data has been saved successfully. If an error happens, display an error indicating the error just happened and don't close the modal to allow users to correct the errors.