Simplify filters to avoid duplication

[dalonsoa]

          These filters are identical to the daily filters and the monthly filters. If they need to be defined on an app basis, I would suggest to:

1. Create utilities/filters.py and put all this filters within JournalFilter and JournalFilterDepth classes.
2. In this file and the corresponding ones in the daily and monthly apps, subclass them:

from utilities.filters import JournalFilter, JournalFilterDepth
class HourlyFilter(JournalFilter):
    """
    Filter class for hourlys that are not Polar Wind, Discharge Curve, or Level Function
    and that have no depth information.
    """

class HourlyFilterDepth(JournalFilterDepth):
    """
    Filter class for hourlys that are not Polar Wind, Discharge Curve, or Level Function
    and that have depth information.
    """

However, if they do not need to be defined on an app basis, just skip step 2 altogether and directly import the JournalFilter and JournalFilterDepth where relevant. The more code we write, the harder it is to maintain, so let's keep it to a minimum.

Originally posted by @dalonsoa in #103 (comment)

[dalonsoa]

No longer relevant.