We were very inconsistent regarding these rules.
Personally I prefer no empty lines around blocks, clases, etc... as
recommended by the Ruby style guide [1], and they're the default values
in rubocop, so those are the settings I'm applying.
The exception is the `private` access modifier, since we were leaving
empty lines around it most of the time. That's the default rubocop rule
as well. Personally I don't have a strong preference about this one.
[1] https://rubystyle.guide/#empty-lines-around-bodies
Generalize the BudgetInvestmentStatus model to Milestone::Status so it
is not specific to budget investments, but can be used for any entity
which has milestones. This is in preparation to make the Milestone
model polymorphic and usable by entities other than budget investments.
