Ignore more Visual Studio files.
Fixes to Xcode archiving.

Don't install auxiliary binaries and libs, otherwise the archive won't
contain just a single app bundle.
Update Gettext.Tools nuget package.

No real changes, but the binaries are stripped and much smaller.
Switch to a different InnoSetup nuget package.

The previous one is not kept up to date and was non-Unicode and didn't
even come with sources repository.  Publish my own InnoSetup package
instead.
Add a Help menu link to GNU gettext manual.
Update version to 1.6beta2.
Fix plural forms help hyperlink not being underlined on OS X.
Add help hyperlink that explains keywords.

Add it to the keywords list in Properties, similarly to the existing
plural forms link.
Fix loosing splitter position on startup.
Reduce ICU data file size.

Replace stock icudt52l.dat with customized version without unneeded
stuff, generated at http://apps.icu-project.org/datacustom/

Removed stuff:

- Charset Mapping Tables
- Rule Based Number Format
- Transliterators
- some misc data:
    - unames.icu
    - zoneinfo64.res
    - supplementalData.res
    - curr/*.res
    - zone/*.res