update instructions for modifying sagenb in HACKING.rst
use sagenb-git instead of sagenb to avoid confusion
remove $ from SAGE_ROOT to improve consistency with Sage docs
Fix a.control-select bug in div#share-publish-buttons for Worksheet and Revisions
Spanish translation completed
A lot of Typos fixed and first comments added
Upload - subir issues fixed
title in links - clave-contraseña and minor typos
Present to infinitive and minor typos
Typos pointed out by  saraedum
messages updated from message.pot
Error when a non-existent (non-void) user is given at login
cancel and invalid user error in admin, adduser
docstring modified
Merge pull request #218 from ppurka/issue-203-doc

update instructions for modifying sagenb in HACKING.rst
Merge pull request #219 from migeruhito/login-error

Error when a non-existent (non-void) user is given at login
Different error messages when adding users
Merge pull request #220 from migeruhito/cancel-adduser-error

Solve issue #210 'Canceling new user creation causes error' and more
kcrisman suggestions
correction to the previous commit