Support a few more statements in PowerShell scripts

Implemented some parts of the AST to allow the following statements to execute:

$path = [System.IO.Path]
$foo -eq $null
10 -ge 4
-not $true
exit

"abc" -match "[ab]"
$matches[0]

function do-this($param1, $param2) { }

try {
} 
catch {
    Write-Host $_.Exception
}