Brazilian portuguese pt-BR improvements

[mniak]

Made some improvements in portuguese translation.

Major issues:

• Wrong translation of signing

Minor issues:

• Use a constructs closer to what is used in a daily basis in portuguese which the users are more used to.
• Fix some unusual casing. In portuguese messages are not written with a capital first letter so often (as it is in english or even more in german).
• Rolled back translation of some technical expressions, like Resource Owner which has its meaning dimmed when translated. Brazilians uses foreign words thorougly.

[johnkors]

I believe @julianpaulozzi made that translation back in the day. Are these changes OK by you, @julianpaulozzi ?

[johnkors]

Published: https://www.nuget.org/packages/IdentityServer3.Localization/0.3.197

[julianpaulozzi]

Yes according to changes. Thanks.