adds custom imap and smtp ports when selecting "Other"

[mikeseese]

This fixes #120 by adding an option in the dropdown for port saying "Other". When selected, it shows an input field for the custom port number

[dweremeichik]

Curious, does it come up correctly if you save the account, and then goes back in to edit it?

[mikeseese]

It seems when I edit an IMAP account, none of the settings other than my name and email on the first window are auto-entered. Even the server/username fields were blank. EVEN if they were auto populated using the existing configuration, the code I propose would not be smart enough to select the Other item in the dropdown and fill the text box

I consider this okay since the other fields are not populated? Could be another issue to populate them in which the Other field would need to be fixed to do such (or ignored).

Another weird note due to react smartness is that if a user inputs a number in the custom field that is in the dropdown, it selects that item in the dropdown (in this case, it doesnt hide the text box - the desired behavior in this case)

[dweremeichik]

Based on nothing else being re-populated, I'm good with this. Nice work, happy hacktoberfest!