Makefile: Whitespace cleanup

Indent our Makefiles using only tabs with width 8.
Also keep all escaped new-lines aligned on column 72. 72 might seem
like a high number but it ensures that the \'s will keep being aligned
without adding realignment noise to patches in the future.
Gitignore: ignore C-stuff

Turning gnome-maps into a C binary produces more intermediate files.
Let's ignore those.
Rename data resource file

Rename the data resource file so that the filename actually contains the
word 'data', indicating what it is.
Make gnome-maps a binary

Make gnome-maps a small C program that loads JS from an included
GResource.

https://bugzilla.gnome.org/show_bug.cgi?id=722338