Add Point cloud loaders (LAS and TXT)

[l-ablaoui]

• Please check if the PR fulfills these requirements

• [ ] The commit message follows our guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

Be aware that the PR request cannot be accepted if it doesn't pass the Continuous Integration tests.

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...) feature

• What is the current behavior? (You can also link to an open issue here) no support in radium to load .las and .txt point clouds

• What is the new behavior (if this is a feature change)? add file loaders for .las and .txt file formats

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?) no

• Other information:

[codecov[bot]]

Codecov Report

Merging #978 (4fc2c2b) into release-candidate (edd1179) will decrease coverage by 0.37%. The diff coverage is 0.00%.

@@                  Coverage Diff                  @@
##           release-candidate     #978      +/-   ##
=====================================================
- Coverage              39.93%   39.56%   -0.38%     
=====================================================
  Files                    345      349       +4     
  Lines                  22928    23146     +218     
=====================================================
  Hits                    9157     9157              
- Misses                 13771    13989     +218     

Impacted Files	Coverage Δ
src/IO/AsciiPCLoader/asciipcloader.cpp	0.00% <0.00%> (ø)
src/IO/AsciiPCLoader/asciipcloader.hpp	0.00% <0.00%> (ø)
src/IO/LasLoader/lasloader.cpp	0.00% <0.00%> (ø)
src/IO/LasLoader/lasloader.hpp	0.00% <0.00%> (ø)

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