Addressed missing includes

[JoshuaSBrown]

This is to fix the problem of inheriting includes from tools, votca/tools#246.
Addressed deepcode warnings.

[ghost]

DeepCode's analysis on #79fc1a found:

⚠️ 1 warning

👉 View analysis in DeepCode’s Dashboard

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[codecov]

Codecov Report

Merging #452 into master will decrease coverage by 0.0%.
The diff coverage is 0.0%.

@@           Coverage Diff            @@
##           master    #452     +/-   ##
========================================
- Coverage    63.3%   63.3%   -0.1%     
========================================
  Files         279     279             
  Lines       22787   22796      +9     
========================================
  Hits        14434   14434             
- Misses       8353    8362      +9     

Flag	Coverage Δ
#gcc	63.3% <0.0%> (-0.1%)	⬇️

Impacted Files	Coverage Δ
src/libxtp/calculators/kmclifetime.cc	0.0% <0.0%> (ø)

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