extra validations for the Link attributes

[LucaV27]

As discussed in a previous (and closed) PR (#99), I created a new PR from the "develop" branch. As the function of updating a GNS3 link was already uploaded in the above branch, I just added a minimum validator for "suspend" and "filters" fields.

[codecov[bot]]

Codecov Report

Merging #104 (d21a73d) into develop (d575625) will decrease coverage by 0.28%. The diff coverage is 77.77%.

@@             Coverage Diff             @@
##           develop     #104      +/-   ##
===========================================
- Coverage    99.85%   99.56%   -0.29%     
===========================================
  Files            3        3              
  Lines          689      697       +8     
===========================================
+ Hits           688      694       +6     
- Misses           1        3       +2     

Impacted Files	Coverage Δ
gns3fy/gns3fy.py	99.56% <77.77%> (-0.30%)	:arrow_down:

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[Krlosromero]

LGTM

[Krlosromero]

Thank you for your PR Luca