Add commands to pull translation from transifex

tx - transifex cli client should be installed in the system.
It's free software and is available in Debian archive.

Run following commands:
1. Init your authorization token
$ make transifex_init

2. Pull translations
$ make transifex_pull

[main]
host = https://www.transifex.com

[beremiz-ide.beremiz]
file_filter = Beremiz_<lang>.po
minimum_perc = 0
source_file = messages.pot
source_lang = en
type = PO