Fix the displayed duration for recordings

Now when the recording has just one playback format, a single duration time will be presented, when have more formats, a list will be presented showing the duration of each format.

refs #1147
Merge branch 'master' into Bug1147
Use :vague time_ago_in_words, don't want it always too precise

refs #1147
Add dotiw locale for en

The gem already adds it, but seems weird to have it for pt-br but not for
en. No problem having it both on the app and gem, though.

refs #1147
Cleaner views to show playback links and duration of recordings

Less text, with focus on the links and the duration. Made it look good both
on the list of recordings and when recordings are shown in the list of
recent activity.

refs #1147
Remove unused strings from locales

refs #1147
Update bigbluebutton_rails and improve names for playback types

Also added code to generate the new structure of playback types on
db:populate.

refs #1147, refs #1142
Update bigbluebutton_rails to improve playback links

Order playback links, showing the default always at the top. Include the
duration only for the first playback link, since they should all have the
same duration. Also improved a bit the dates shown with the recordings.

refs #1142
View and controller to edit playback types

Overriding the controller from BigbluebuttonRails to implement our own
authorization restrictions and a new action #index to show all playback
types and allow admins to edit them.

Includes an update on BigbluebuttonRails

refs #1142
Merge pull request #45 from mconf/Bug1147

Fix the displayed duration for recordings and improve playback names for recordings.

refs #1142, refs #1147