Fix helper token escape handling and unescaping when unquoting strings

[jasmith-hs]

Allows {% cycle 'a','class=\'foo bar\'' %} to be interpreted correctly by splitting properly and not trying to split into 'a',;class=\'foo and bar\''.

Replaces calls to WhitespaceUtils.unquote with WhitespaceUtils.unquoteAndUnescape to properly unescape quoted strings.

This fixes escaping and unescaping in the following tags:

• {% cycle %}
• {% extends %}
• {% from %}
• {% import %}
• {% include %}
• {% block %}

Previously this would fail to render:

{% for item in [0,1] %}{% cycle 'a','class=\\'foo bar\\'' %}.{% endfor %}

And the following would render incorrectly:

{% for item in [0,1] %}{% cycle 'a','class=\\'foobar\\'' %}.{% endfor %}

Rendering as a.class=\'foobar\'. instead of a.class='foobar'.