Complex Number Support 2

[xtalax]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the ScioML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Adds complex number support, does this by splitting the system in to real and imaginary parts.

fixes #58
fixes #101

depends on SciML/PDEBase.jl#22

[codecov]

Codecov Report

Attention: 11 lines in your changes are missing coverage. Please review.

Comparison is base (a04e094) 83.02% compared to head (e240a06) 84.79%.
Report is 40 commits behind head on master.

Files	Patch %	Lines
src/interface/solution/common.jl	21.42%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #342      +/-   ##
==========================================
+ Coverage   83.02%   84.79%   +1.76%     
==========================================
  Files          40       41       +1     
  Lines        1756     1960     +204     
==========================================
+ Hits         1458     1662     +204     
  Misses        298      298              

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