PHYLO web should allow all usernames that OpenPhylo does

[movermeyer]

If a user registers a new account in the OpenPhylo UI, they won't be able to log into the PHYLO web game if the username contains special characters.

Steps to reproduce:

1. Got to OpenPhylo's User registration page
2. Register with a username that contains a '_' character (ex. "my_user")
   • Registration works fine. This is correct.
3. Go to the PHYLO web game
4. Click "Login"
5. Try to enter your chosen username

It fails since the username field of the PHYLO game doesn't allow you to enter underscores.

The PHYLO game's username input field should allow all the characters that the OpenPhylo registration allows.

This is especially true of underscore characters, since the Phylo web game is already using underscores in the guest user account names (ex. "guest_HJBIkp").

Tested with PHYLO Web v2.0.1