Update PowershellSyntax.tmLanguage

Fixes several issues:
229: Correctly highlights the operators -clt, -cle, -cgt, cge
235: Fixes issues highlighting paths with symbols in them
259 & 265: Fixes issues with operator highlighting, such as -NoTypeInformation being incorrectly highlighted as two elements, but allows for -Not1 to be correctly interpreted as two elements
393: Allows for permissible symbols in command names