Fixes for pgAdmin4 messages

Hello,

While translating the messages, I encountered some English messages,
that I think should be fixed.
Please consider applying the attached patches.
If you have any concerns or questions, I'm ready to explain all the
fixes proposed.

And I have a question - do you use some kind of style guide?
(Something like:
https://www.postgresql.org/docs/10/static/error-style-guide.html)
In particular, I'm confused with such messages:
This URL cannot be called directly!
This URL cannot be called directly.
...
Name must be specified.
Name must be specified!
...
Are there any reasons to use exclamation marks in some of the messages?
And if so, in which messages exactly they should be used?

Best regards,
------
Alexander Lakhin
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company