Positional sugar for operators that usually take one arg

[appsforartists]

The named arguments pattern is great for functions that take multiple arguments. We moved all operators to it in #193. However, there are some operators that usually take a single argument; they have been made harder to read and to use by the transition.

Therefore, I'm going to go back and add positional sugar for operators with one primary argument:

• added/subtracted/multiplied/dividedBy
• distanceFrom
• log
• pluck
• isAnyOf
• rewriteTo
• threshold
• startWith
• merge
• appendUnit
• _map
• _tap
• _filter
• _slidingWindow

For consistency, they will keep their named argument signatures as the primary entry. The positional alternative is just sugar, because this:

translate$.distanceFrom({ x: 100, y: 100 }).threshold(70).isAnyOf([ ThresholdRegion.ABOVE ]).rewriteTo(100);

is easier to read and to write than:

translate$.distanceFrom({ origin: { x: 100, y: 100 } }).threshold({ limit: 70 }).isAnyOf({ matches: [ ThresholdRegion.ABOVE ] }).rewriteTo({ value: 100 });