Client cannot be made without all attributes being present

[autumn-sonata]

Here is an example user command that exhibits this behaviour:

add n/John Doe a/311, Clementi Ave 2, #2-25 i/$1000 m/$200 r/HIGH ip/Savings Plan c/CURRENT t/friends t/owesMoney

In this example, the phone and email attribute is taken out of the client. An Invalid command format! is being returned via the result display:

In a real world scenario, the financial advisor may not know the full details of the client first, and thus will need to have an appointment. It may be frustrating to know that I have a client that I want to add to the planner and mark down an appointment to meet up with, but I cannot due to not having the full details of the client.

Allowing a variable number of details (with the name and one other field for point of contact being fully compulsory), I can better manage clients that may have some details missing.