Create new variable modifier for truncate strings

[rafageist]

So far (div 4.9), the way to truncate a string of characters is:

{strip}{$varname}{/strip}
(# trim("{$varname}") #)

We are thinking of implementing a variable modifier, but we are left to analyze if it really is necessary and good.

ltrim: {-varnme}
rtrim: {varname-}
trim: {-varname-}
trim: {trim:varname}
trim: {$varname:trim}