More user-friendly voting input validation error messages

[chauey]

Minor enhancement.

Expected behaviour

User-friendliness includes error messages and if user picks too many users to vote for, would expect an error message non-technical people would understand better. Instead of "... Array is too long...", perhaps something like "You can only vote for 33 delegates at a time. 34 were selected."

Actual behaviour

Steps to reproduce

Choose over 33 delegates and try to vote for them

[slaweet]

Before the migration, we had check that disables the "Confirm" button if more than 33 delegates are selected. We should get it back now.

There is an enhancement issue scheduled for the next version to give more aggregated info about selected delegates #445 That should help.