Optimize the process of reading .seq files

[beorostica]

This pull request is the continuation of the work done by @gabuzi in the pull request #238.
It is also intended to address the issue #224.

[codecov]

Codecov Report

Attention: 63 lines in your changes are missing coverage. Please review.

Comparison is base (e3107c1) 92.60% compared to head (efadc1a) 90.50%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #301      +/-   ##
==========================================
- Coverage   92.60%   90.50%   -2.11%     
==========================================
  Files          33       33              
  Lines        2245     2411     +166     
==========================================
+ Hits         2079     2182     +103     
- Misses        166      229      +63     

Flag	Coverage Δ
base	92.00% <0.00%> (-0.68%)	⬇️
core	90.47% <ø> (ø)
files	83.84% <64.59%> (-8.51%)	⬇️
komamri	93.89% <ø> (ø)
plots	93.28% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
KomaMRICore/src/KomaMRICore.jl	100.00% <ø> (ø)
KomaMRIFiles/src/KomaMRIFiles.jl	100.00% <ø> (ø)
KomaMRIBase/src/datatypes/sequence/ADC.jl	92.50% <0.00%> (-2.38%)	⬇️
KomaMRIBase/src/datatypes/sequence/Delay.jl	85.71% <0.00%> (-14.29%)	⬇️
KomaMRIBase/src/datatypes/sequence/Grad.jl	89.83% <0.00%> (-1.55%)	⬇️
KomaMRIBase/src/datatypes/sequence/RF.jl	85.45% <0.00%> (-1.59%)	⬇️
KomaMRIBase/src/datatypes/Sequence.jl	91.31% <0.00%> (-0.60%)	⬇️
KomaMRIFiles/src/Sequence/Pulseq.jl	82.10% <64.59%> (-9.01%)	⬇️

[cncastillo]

No need to create a new pull for this. Continue in #238.