[i18n] New translate structure

Dear translators,

As some of you already have noticed, we recently changed the structure
of the calcurse project on Transifex. Instead of one massive resource
containing all strings, there now is one main resource for the calcurse
binary itself and a lot of others for the online help texts [1].

We imported the binary strings into the new calcurse resource, so that
updating them boils down to adding newly introduced strings. However,
you will need to migrate translations for online help texts manually.
They have undergone following changes:

* One Transifex resource per help text.
* One string per paragraph instead of one string per help text.
* Lots of minor typo fixes and small additions.

You can use former translations, split them into chunks and check for
changes, if you want to.

The easiest way to get all the new message catalogs is pulling from
current master. The main source file is po/calcurse.pot, the sources for
the online help texts are now located in po/doc/.

If you use transifex-client, you can use following work flow to
translate the help text files:

    $ cd po/doc/
    $ msginit -i pipe.pot -o pipe-de.po -l de --no-translator
    $ poedit pipe-de.po
    $ tx push -t -r calcurse.doc-pipe -l de

You can replace "pipe" by any other help text file and "de" by the
language you are translating into (and the poedit(1) invocation can be
replaced by any other tool you use to translate, of course).

If there are any questions concerning the new structure, feel free to
ask here.

Thank you for all your awesome work.


[1] https://www.transifex.com/projects/p/calcurse/resources/