fix dark theme preference incorrectly storing the "No" option

Added alternative dark theme

It is finally here: Dark theme for the whole Trello interface.

This version includes Sticky Cards. This feature is still in Beta, so use with caution.

In order for it to work, you have to:
- enable it in plugin settings (click on Trelloimprovements link in Trello header, then check this feature)
- it will work on boards where you have the permission to move cards
- add :TI-sticky: to card title that you want to stick to the top of the list

Known limitations:
- please have only one sticky card per list, for now
- using this with built-in Trello auto-sorting features is not advised. So, if you use sort by card age, please do not use this feature as well

removed feedback.html from addon, minor styling improvements

Asking addon users to fill in a survey. Thank you!

Fixed global card counting Settings

Fixed version number. Made cross browser compatible - now supports Chrome as well. But we all love Firefox here :)

Added link to plugin website.

It is now possible to turn card IDs On and Off

It is now also possible to enable/disable card global and list card counter.

Fixed saving settings.

This is version 1.0.

For the first time, I have introduced settings panel. Right now it has one single simple setting, but I hope to add more as I implement more features.

The setting itself will switch the way labels are shown:
- if disabled (default) they will be slightly larger and label name will be shown in the card as in versions up till now.
- if enabled, label will be hidden and label's color will be used as background color for the whole card

Updated to latest Firefox addon SDK