new attachment model
add file upload related terms in activity stream
add and update views and templates for attachments
Merge branch 'develop' into feature/uploading
fix file upload and update
fix deleting file
Merge branch 'develop' into feature/uploading

Conflicts:
	gasoline/views/document.py
add attachments view, add delete icon, print pretty filesize
fix delete attachments, redirect to attachments view after delete or upload
Merge branch 'feature/uploading' into develop
split document template in three blocks
compile translation with makefile