Regenerate the POT file and pull new translations from Transifex.

Also, update the Transifex URL in the configuration file:
transifex.net has redirected to transifex.com for some time,
and now its certificate has expired.

Rename the 'tests' directory to 'ipa-tests', and create an ipa-tests RPM
containing the test suite

Part of the work for: https://fedorahosted.org/freeipa/ticket/3654

Patch generated by:
  cd install/po
  make pull-po
  make update-po

Generated by running `make update-pot` in install/po

Update the pot file to match current source, and pull
translations from Transifex

The commands used to create this commit were:
  tx pull -fa  # needs an account and transifex client setup
  cd install/po
  make update-pot
  (update LINGUAS to contain all languages with translations, and no empty ones)
  make update-po

The .po files we use for translations have two shortcomings when used in Git:
- They include file locations, which change each time the source is updated.
  This results in large, unreadable diffs that don't merge well.
- They include source strings for untranslated messages, wasting space
  unnecessarily.

Update the Makefile so that the extraneous information is stripped when the
files are updated or pulled form Transifex, and empty translation files are
removed entirely.
Also, translations are normalized to a common style. This should help diffs
and merges.

The validator requires file location comments to identify the programming
language, and to produce good error reports.
To make this work, merge the comments in before validation.

First patch for: https://fedorahosted.org/freeipa/ticket/2435