String mutator

[richardwerkman]

Is your feature request related to a problem? Please describe.
We could add mutations to string-type method calls. I was thinking about these:

Original	Mutated
EndsWith()	StartsWith()
StartsWith()	EndsWith()
Trim()
TrimEnd()	TrimStart()
TrimStart()	TrimEnd()
Substring()
ToUpper()	ToLower()
ToLower()	ToUpper()
ToUpperInvariant()	ToLowerInvariant()
ToLowerInvariant()	ToUpperInvariant()
PadLeft()	PadRight
PadRight()	PadLeft()
ElementAt()
ElementAtOrDefault()
Min()	Max()
Max()	Min()
MinBy()	MaxBy()
MaxBy()	MinBy()

Do all of these make sense? And am I missing some?