Arranged fields order in ServiceSubscriptionPayment ModelAdmin
Moved EMAIL settings from dist settings file to default settings file
Changed Payment action text
Inverted ServiceSubscription managers (for admin), changed algorithm to find insolutes
Default mail sender set in default_settings
Created PercentageDecimalForm field to manage decimal fields containing a percentage.
 Changed cancel action behaviour on ServiceSubscription admin
Translation of invoice models
Added default mail template for the insolutes
Mail and admin actions (read well)

Changed EMAIL_TEMPLATE from srtring to dict (for multiple templates).

Bug found in admin actions inserted from get_actions(): gives typeerror
"takes exactly 3 arguments (4 given)". Actions added allusers-wide,
superuser check done into any single action (actions will be visible
to any user, though ).
Overrided get_queryset() for ServiceSubscription: superuser sees all_objects,
 other users see objects.
Fixed some bugs on insolute mail production logic.

Added translation into the mail template.