Hop i18n

[Matt Casters <ma...@neo4j.com.INVALID>]

Dear Hop devs,

Digging into the Hop Translator as part of HOP-2378
<https://issues.apache.org/jira/browse/HOP-2378> I found a lot of things
rotten in the state of the i18n translations.
I found a lot of keys were not provided for the English/US locale.

To help out I finally improved the code scanner/crawler to the point where
it will recognise i18n keys in all situations and it will now also pick up
"i18n:package:key" specifications across the codebase for use in
annotations.

It was quite a bit of work to get everything cleaned up over the past
week(s).
So please do me a favor and review PR 547
<https://github.com/apache/incubator-hop/pull/547> and take a look at the
short doc I wrote for it:

http://hop.apache.org/dev-manual/latest/internationalisation.html

Translator now starts with 0 warnings for en_US.  Packages with missing
translations are shown in a light-gray over dark-gray all the way to red
(all missing) in case you're wondering.  Simply click on a highlighted
package on the left and provide the missing string for the selected key.

Thanks in advance!

Cheers,
Matt