Add Maki icons

This patch makes use of the Maki point of interest icon set
from MapBox. The icons are BSD licensed.

https://bugzilla.gnome.org/show_bug.cgi?id=720250
place: make icon property read-only

The icon for a place is now derived from its type. Having the icon
property READWRITE does not make sense.

https://bugzilla.gnome.org/show_bug.cgi?id=720250
Add forgotten part of gettext commit (fbdd8d4)

Remove intltool references from DISTCLEANFILES and EXTRA_DIST.
icons: Fix paths

Fixes `make dist`.
Release 3.11.4
Revert "icons: Fix paths"

This reverts commit f9775b538ba544936de5d78cdeaea4bc937b3293.

This patch broke installation of icons.

https://bugzilla.gnome.org/show_bug.cgi?id=722205
icons: Fix paths

This time fix `make dist` without breaking icon installation.

https://bugzilla.gnome.org/show_bug.cgi?id=722205
Release 3.11.4.1