Expanded the external-link-script with a css-class
Change to upload scripts requested by Clement

I'm correcting the epidb upload script for our country and I figured that the Q15 (intake) not collected in our country.
It is not possible to provide a NULL value for Q15_*. Can you change the definition of the columns to accept NULL value for non mandatory (Q15 at least) questions ?
Merge remote branch 'origin/master'
revamped cohorts script to allow for general set of control/measurement variables
Added cache killer templatetag
Merge remote branch 'origin/master'
Neighborhood maps work 'centered on user' if no gid is in the request too
Bugfix on prev. commit
Mobile interface: restrict to non-deleted users
Textual changes in the registration process
bug fix in cohorts script
add option for additional conditions in cohorts script
Merge branch 'master' of https://github.com/vanschelven/epiwork-website
Danish translations
Danish language is 'da', not 'dk'
Modified cookie-setting translation
Using Klaas' version of requirements for 'registration'
Username is max 30 chars; fixed bug when copying in email into username
Merge remote branch 'origin/master'
New version of collection script, with changes as indicated by Daniela