Adaptations in shared stylesheets to pline nice in different projects

Some changes have been made to adapt the _config.sass and _kits.sass:

* Added Facebook blue palette
* Created facebook blue gradient
* Some variables are defined with !default to allow per-project customizations before include the _config.sass
Defaulted font-size
Added to color palette and gradients several browns and goldens
Added darker red
Added mixin to display a centered popup
Added metal colors: $gold, $silver & $bronze
Renamed -team-color to -team-color to conform aur consensed naming
Add another gray gradient
Add many stripped gradients used in the match summary
Added several gradients, mosrtly stripped gradients
.kit-player class must be relative by default
Use a more specific class for trapezium halves
Add a couple more gradients
Moved to the config file styles related to floating modals
I think that modals/popups stuff belongs only to the desktop app