dtypes in intervals table

current encoding of types:

start_time float64
stop_time float64
duration object
end_frame object
flashes_since_change object
image_index object
image_name object
image_set object
is_change object
omitted object
start_frame object
stim_block object
stim_name object
tags object
timeseries object
dtype: object

suggestion:

start_time float64
stop_time float64
duration float64
end_frame int
flashes_since_change int
image_index int
image_name object (string)
image_set object (string)
is_change bool
omitted bool
start_frame int
stim_block int
stim_name object (string)
tags object ?
timeseries object ?