fix: Turtle.js.pathData returns NaN paths ( fixes: #339, fixes: #336, fixes: #337, fixes: #338 )

[ninmonkey]

Turtle.js.get_heading was returning NaN which broke output of Turtle.js.ToHTML

This fixes: #339 , #336 , #337 , #338

original error

turtle.html:159 Uncaught TypeError: turtle.pathData is not a function
    at draw (turtle.html:159:28)
    at turtle.html:167:1
draw @ turtle.html:159
(anonymous) @ turtle.html:167

Test case

$turt = turtle square 42 stroke blue fill salmon opacity 1.0
$turt.PSTypeNames.Insert(0, 'Turtle.Js')
$turt.ToHTML() | Set-Content -Path  'turtle.html'
Get-Item 'turtle.html' | Get-Item | Invoke-Item

[StartAutomating]

@ninmonkey I'll take this PR but ToHTML was removed (too prescriptive for this point of development)