Adds a safe check, i18n is expecting undefined not null. Fix a method name and translation to be at placeholder.

Removing translateString forces using data-i18n attributes, to make sure we do not forget to set them. Missing data-i18n attributes is a problem with late loading where we can end up without translation, without text. Missing data-i18n attributes is also problem that strings will not be translated when changing language.
Fixes a bug in invite dialog, where remove password button was shown for non moderators.

Converts ConferenceUrl to a class and binds an instance to the global
APP variable, as requested by HTerezov.

Is not very readable and is not used across the project

We need to make sure that on the page reload all original parameters
used to load the conference are preserved. New modules helps to manage
different types of conference URLs like the one used for invites and
the one for reloading the page.

Remove check for the call overlay being visible in postponing
the toolbar being hidden, as we don't want to have it displayed at all
when the overlay is there.

Will disconnect on ConferenceErrors.VIDEOBRIDGE_NOT_AVAILABLE.
Show the same message when either JVB is not available or Jicofo
disconnects.

We pass key which is enough to obtain the title.

Fixes issue of method 'setTooltip' in modules/UI/util/UIUtil.js: Excluded 'Uncaught TypeError':
```
UIUtil.js:134 Uncaught TypeError: Cannot read property 'setAttribute' of null
```