.src and .ui gettext migration

[Caolán McNamara]

So, I'm pretty happy with my latest iteration of migrating to gettext
and I've got it up and running on all supported platforms.

backstory is https://lists.freedesktop.org/archives/libreoffice/2017-Ma
y/077818.html with the modification that we retain a msgctxt, albeit a
shorter one than the current pseudo msgctxt that is generated for the
current .po files

To try and minimize disruption I've a script available in master as
solenv/bin/update-for-gettext to update our current translations to
give them a new msgctxt (and update their keyid comment) 

I've successfully run this over the sample tarball of .pos extracted
from pootle that cloph provided. i.e.
python2 /path/solenv/bin/update-for-gettext translations/libo_ui
It shrinks and normalizes the msgctxt and updates the keyid comment for
.src and .ui strings and moves them into a per-module messages.po.

For .src strings the msgctxt typically becomes the 2nd line of the
current msgctxt i.e. the #define of the string or stringarry

For .ui strings the msgctxt typically becomes uifilename|widgetname

(caolanm->cloph: will this script suffice for getting pootle updated ?)

In our code I've autogenerated matching initial contexts for the
matching .ui and .hrc source strings.

(newly added strings can have arbitrary meaningful context strings
e.g. NC_("papersize", "A4") its just the existing ones that will have
ones mechanically generated from the existing metadata available)

Is there any outstanding concerns or questions.