Inline getTotalCategoryAuthorsSelected()

I also renamed the local variable which references the function
from the property "selected-authors-prediction"
from getTotalAuthorsSelectedPredicted()
to getTotalAuthorsSelectedInCategory().
Delete unused function getTotalCategoryAuthorsSelected()
Rename getTotalCategoryAuthors() to getTotalAuthorsInCategory()
Remove duplicate subscription
Rename updateFilters() to initOrUpdateFilterLists()
Use getTotalCategoryAuthors() from filter-utils in filter-authors

I removed the duplicate implementation of the function,
now that the two functions have actually become identical.
Prepare to add new utility function incrementProperty in utils

I defined the function signature based on the expected usage
in two different places: in filter-authors to increment a
property by 1 and in prepare-predictive-filters to increment
a property by given multiplier.
Move definitions of no() and or() near the beginning

I intend to use or() to handle an optional parameter
in incrementProperty().
Complete implementation of incrementProperty()
Use utility function incrementProperty() in place of similar code