Version all installed files

[achadwick]

This should address the remaining aspects of #92 from the limited perspective of what gets installed. Please could everyone with a stake in this (@mitchfoo, @schumaml, @mypaint/developers, @mypaint/packagers) offer a speedy review so that I can merge the consequences of this rather far-reaching change into mypaint, libmypaint.deb, and MINGW-packages?

The resulting install layout within a prefix is as listed below, which allows multiple side-by-side libmypaint installations at the minor API version as requested by @mitchfoo.

Note to self: the gettext domain has changed. I'll need to check this actually works, with the right tweaks, in MyPaint proper so that I can discount the stuff that glib and gtk do as being from the bronze age. Are hyphens and dots in gettext domains acceptable?

lrwxrwxrwx ./lib/libmypaint-2.0.so -> libmypaint-2.0.so.0.0.0
-rwxr-xr-x ./lib/libmypaint-2.0.la  
-rw-r--r-- ./lib/girepository-1.0/MyPaint-2.0.typelib  
-rwxr-xr-x ./lib/libmypaint-2.0.so.0.0.0  
-rw-r--r-- ./lib/pkgconfig/libmypaint-2.0.pc  
lrwxrwxrwx ./lib/libmypaint-2.0.so.0 -> libmypaint-2.0.so.0.0.0
-rw-r--r-- ./include/libmypaint-2.0/mypaint-config.h  
-rw-r--r-- ./include/libmypaint-2.0/mypaint-brush-settings-gen.h  
-rw-r--r-- ./include/libmypaint-2.0/mypaint-brush.h  
-rw-r--r-- ./include/libmypaint-2.0/mypaint-surface.h  
-rw-r--r-- ./include/libmypaint-2.0/mypaint-tiled-surface.h  
-rw-r--r-- ./include/libmypaint-2.0/mypaint-rectangle.h  
-rw-r--r-- ./include/libmypaint-2.0/mypaint-brush-settings.h  
-rw-r--r-- ./include/libmypaint-2.0/mypaint-mapping.h  
-rw-r--r-- ./include/libmypaint-2.0/mypaint-fixed-tiled-surface.h  
-rw-r--r-- ./include/libmypaint-2.0/mypaint-glib-compat.h  
-rw-r--r-- ./share/locale/[...]/LC_MESSAGES/libmypaint-2.0.mo 
-rw-r--r-- ./share/gir-1.0/MyPaint-2.0.gir  

[achadwick]

No objections so far...