Contact Unit tests authenticated

[Rahul-JOON]

This PR aims to solve issue #271.

The following changes were made:

1. Overall changes:

• all pytests were reworked and input and expected values were handcrafted.
• added calculations and verification methods as comments

2. File-specific changes

• tests_contact_common_functions:
  - corrected names of variables
  - for the '_find_min_dist' test, arbitrary close lines and away lines were combined into a single test and test case for
  parallel lines were added
  - point to be noted: find min dist function returns -1 for contact point of system 1 if the lines intersect
• test_contact_specific_functions:
  - Common rod and cylinder were initialized for tests.
  - test only assess the working of function with contact forces and many initial conditions were added (ex: stationary
  systems and zero initial forces) for easier calculations.
• test_wrapper_classes:
  - correct initialization of rod and rigidbody.
  - test values were copied from specific function pytests.

If the tests are acceptable, we can make more tests that are not 'nu' independent.

Also, can we remove the elif block at https://github.com/GazzolaLab/PyElastica/blob/master/elastica/joint.py/#L574, I think this code is redundant as 'i' never equals 'n_points'.

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -0.55 ⚠️

Comparison is base (baea843) 94.72% compared to head (0f3a92e) 94.17%.

❗ Current head 0f3a92e differs from pull request most recent head 5226332. Consider uploading reports for the commit 5226332 to get more accurate results

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Additional details and impacted files

@@               Coverage Diff                @@
##           update-0.3.2     #274      +/-   ##
================================================
- Coverage         94.72%   94.17%   -0.55%     
================================================
  Files                43       43              
  Lines              2938     2938              
  Branches            341      341              
================================================
- Hits               2783     2767      -16     
- Misses              122      134      +12     
- Partials             33       37       +4     

Impacted Files	Coverage Δ
elastica/joint.py	85.76% <0.00%> (-5.18%)	⬇️

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[bhosale2]

Minor doubt.

[bhosale2]

@Rahul-JOON I will review once again, once @armantekinalp and @Ali-7800 s comments have been addressed.

[armantekinalp]

Some typos

[armantekinalp]

LGTM

[Ali-7800]

LGTM

[bhosale2]

LGTM