[icedtea-web][rfc] Polish localization and other messages cleanup

[Adam Domurad]

> [...]> Error! Items equals for: CPJVMPluginAllowTTValidation = Allow type-time validation
> [...]
>
> Please, anybody help me out here: What is "type-time validation"?

Hi, in icedtea-web settings, you may choose a JRE, and perform some
basic validation that you picked a valid folder. This checkbox refers to
the location of Java being validated right when you choose it, or, in
the case of typing it, providing feedback as you type it out. I think
you can interpret this as "Automatic JRE validation" or similar.

>
> Thank you!
>
> Jacob

Happy hacking,
-Adam