Infix operators and paranthesis precedence

[gustaphe]

I headed out to add some infix comparison operators, but wasn't happy to have to defend keeping the weird parenthesis issues, so I fixed that too.

List of infix comparison operators

These are the ones currently in the comparison dictionary:

Closes #168
Closes #239
Closes #279
Does much of #246

[codecov]

Codecov Report

Attention: Patch coverage is 85.13514% with 11 lines in your changes missing coverage. Please review.

Project coverage is 82.01%. Comparing base (1577e93) to head (86d9460).
Report is 12 commits behind head on master.

Files	Patch %	Lines
src/latexoperation.jl	82.81%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #296      +/-   ##
==========================================
+ Coverage   77.81%   82.01%   +4.19%     
==========================================
  Files          21       21              
  Lines         834      873      +39     
==========================================
+ Hits          649      716      +67     
+ Misses        185      157      -28     

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[gustaphe]

Will probably need to forgo "\forall", it's not valid in 1.6