Upload party avatar documentation

[lykmapipo]

From @kasongoyo on September 13, 2018 12:40

Can you share how does API handle avatar upload?

Copied from original issue: CodeTanzania/emis-asat#5

[lykmapipo]

@kasongoyo Its work on progress...thanks for point it out.

[kasongoyo]

I thought we forgo this feature?