correct hash syntax to pass rubocop
change to work with Array

Conflicts:

	lib/grape/validations/mutual_exclusion.rb
change to work with optional scope

Conflicts:

	lib/grape/validations/at_least_one_of.rb
	lib/grape/validations/mutual_exclusion.rb
	lib/grape/validations/params_scope.rb
add base class for several params method validation

Conflicts:

	lib/grape/validations/at_least_one_of.rb
	lib/grape/validations/mutual_exclusion.rb
correct some syntax to pass rubocop

Conflicts:

	lib/grape/validations/params_scope.rb