Add Summaryslice interval iterator helper

This adds a new type called SummarysliceIntervalIterator which allows to iterator over chunks of timeslices of a given time interval. This is useful if someone wants to analyse e.g. 30 second intervals. The summaryslices are returned as Vector{Summaryslice} and are time-sorted as well.

test/tools.jl

@@ -336,3 +336,20 @@ end
     @test π/2 ≈ angle(Direction(1.,0,0), Direction(0.,0,1))
     @test π ≈ angle(Direction(1.,0,0), Direction(-1.,0,0))
 end
+
+
+@testset "SummarysliceIntervalIterator" begin
+    f = ROOTFile(datapath("online", "summaryslices.root"))
+
+    sii = SummarysliceIntervalIterator(f, 2)
+    suslis = collect(sii)
+    @test 55 == length(suslis)
+    @test 0 == length(suslis[1])
+    @test 1 == length(suslis[2])
+    @test 2 == length(suslis[3])
+    @test all(20 .== length(suslis[3:end-2]))
+    @test 8 == length(suslis[end-1])
+    @test 6 == length(suslis[end])
+
+    close(f)
+end