Makefile: Add suport for multiple locale builds
Makefile: Add suport for multiple locale builds

* When building the xpi file include documentation files in all available languages

* When packaging documentation files, first copy the English version of
  the files, then overwrite them with the translated language specific ones.

derenio/vimperator-labs,stemar94/vimperator-labs,seanmorton/vimperator-labs,Quicksaver/vimperator-labs,paretje/vimperator-labs,airodactyl/airodactyl,Sheile/vimperator-labs,airodactyl/airodactyl,Evidlo/vimperator-labs,mcarton/vimperator-labs,Sheile/vimperator-labs,zklinger/vimperator-labs,seanmorton/vimperator-labs,Evidlo/vimperator-labs,stemar94/vimperator-labs,zklinger/vimperator-labs,Quicksaver/vimperator-labs,nullren/vimperator-labs,mcarton/vimperator-labs,nullren/vimperator-labs,paretje/vimperator-labs,derenio/vimperator-labs