Mandatory fields in Add New Stock form

[anandarupmukherjee]

Addresses #16

[tobyaharris]

I'll look at applying this to all the forms in the solution. Working list of them:

• Order form
• Withdrawal form
• Stock Check form
• New stock form - original and working

[tobyaharris]

Look at this! Love it. If any fields are left blank, when Submit is clicked this message is shown against the first blank field. Great!

[tobyaharris]

The Stock Check form can't fail, except for:

• no location is selected, which is handled ~ok

-The field is emptied, in which case the Units updated successfully! popup is displayed but no withdrawal event is logged.

[tobyaharris]

@anandarupmukherjee I'll need your help with this

[tobyaharris]

^ undid my unhelpful attempts. The bit that's working is going out the door, the bit that isn't will wait.