Fix sovereignty bonus on tower strontium consumption and improve algo

[warlof]

• Add sovereignty bonus to the strontium consumption
• Replace hard code fuel/stront reduction if tower are in sovereignty by 0.75 rate
• Merge fuel and stront consumption in a global array
• Replace the if/elseif/else statement which check the tower size by a lookup into a global consumption array

[Zumochi]

This is nice but it also needs faction towers. The page on the Evelopedia is still accurate AFAIK to use as source: https://wiki.eveonline.com/en/wiki/Starbase#Fuel_Usage

[MilosRasic]

$tower_size = $tower_type_name[3];

is not a good was to get tower size, because of already mentioned faction towers but especially since Large towers won't have Large in the end. A quick and dirty fix:

            $tower_size = $tower_type_name[count($tower_type_name) - 1];
            if ($tower_size == 'Tower')
                $tower_size = 'Large';

[warlof]

Well, faction tower are not yet take in charge. So not fault of my commit. I'm working on an improvement.

[warlof]

fix in #400