Additional account validation added

[lexfrl]

fixes #127

[ltfschoen]

I think it would help to disable the Next Step button by default and enable it in a different colour when all the input fields are valid.

I also think we should highlight what form fields still need to be completed before the Next Step button will be enabled.

[Tbaut]

We will not do a release for this fix. The release will be done for the next feature that we expect to have which is Bip39 support.

[lexfrl]

I think it would help to disable the Next Step button by default and enable it in a different colour when all the input fields are valid.

I also think we should highlight what form fields still need to be completed before the Next Step button will be enabled.

It's just a quick fix for the exact annoying issue. If it doesn't makes the app any better - we can just leave it as it is and close this PR.

[maciejhirsz]

Code LGTM

[ltfschoen]

I just tried these changes and they work great!