Allow admins to view past-due subscriptions.
Some refactoring of displayed of past-due subscriptions.
And removing comment..
Fix typo in test name.
Minor tweaks.
Consider pending & past due subscriptions as 'active' in the sense that they should prevent one from adding a new subscription.
Merge branch 'develop' into feature/billing-past-due-subscriptions
Admins can cancel pastdue subscriptions, but users cannot cancel their own pastdue subscription, as then admins won't be able to search for them.
detect os in browser and show proper download link

We add a class to the html element based on the detected os and use that to pick which download link should be visible.

If we detect an os that is not supported we display a deactivated download link instead with all alternatives.
Merge pull request #99 from azul/feature/os-detection

detect os in browser and show proper download link
Add permissions to subscriptions index, and fix test to stub the subscription's balance.
remove leftover from testing os specific sections
use latest version of srp_js to fix #4002

We were not encoding the srp password properly before. So umlauts in the password would cause the login procedure to fail.
blacklist system logins for aliases and logins

We blacklist based on three things:
* blacklist in APP_CONFIG[:handle_blacklist]
* emails in RFC 2142
* usernames in /etc/passwd

The latter two can be allowed by explicitly whitelisting them in APP_CONFIG[:handle_whitelist].

We stick to blocking names that have been configured as both blacklisted and whitelisted - better be save than sorry.
Merge pull request #100 from azul/feature/os-detection

remove leftover from testing os specific sections
Merge pull request #101 from azul/bugfix/4002-utf8-encode-srp-password

use latest version of srp_js to fix #4002
Merge pull request #102 from azul/feature/3602-email-blacklist

blacklist system logins for aliases and logins
Some cleanup of code to deal with past due subscriptions.
Merge pull request #98 from jessib/feature/billing-past-due-subscriptions

Feature/billing past due subscriptions
Make download links configurable

This way we won't have to redeploy once the new links to the windows and the android version are there.

Also this obviously offers more flexibility for providers.