Fix complex if operators

[dantti]

Without this fix comparing a simple QString
to a string hardcoded on template fails,
it also fixes when the string is a QByteArray
so that this renders "true" if foo is either a
QString("foo") os a QByteArray("foo")

{% if foo = 'bar' %}true{% endif %}
or
{% if 'bar' = 'bar' %}true{% endif %}

[codecov-io]

Current coverage is 69.70%

Merging #23 into master will decrease coverage by -0.35% as of 33c2f88

@@            master    #23   diff @@
=====================================
  Files          158    158       
  Stmts         9753   9838    +85
  Branches         0      0       
  Methods        235    224    -11
=====================================
+ Hit           6832   6858    +26
  Partial          0      0       
- Missed        2921   2980    +59

Review entire Coverage Diff as of 33c2f88

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[steveire]

This commit does many different things. Please split it into multiple commits each with a commit message explaining why it should be added (eg compare to python/django behavior).