Feature refine RPC & pan sharpen

[dugalh]

Features:

• Add RPC model refinement with GCPs.
• Add Gram-Schmidt pan sharpening.
• Round and clip image data when necessary, before writing to file.
• Refactor utils module to common.
• Copy RGB* source colour profile to output image.
• Tighten parameter file validation and improve error handling in CLI & thread pools.

Fixes:

• Change duplicated short form CLI options.
• Improve downsampling of test images.

Docs:

• Re-organise the CLI getting started section.
• Add docs for RPC refinement, pan sharpening and GCP file formats.

Tests:

• Add and update tests & data for RPC refinement and pan sharpening.

[codecov]

Codecov Report

Attention: Patch coverage is 90.81365% with 70 lines in your changes missing coverage. Please review.

Project coverage is 93.05%. Comparing base (1c06df6) to head (821395e).
Report is 94 commits behind head on main.

Files with missing lines	Patch %	Lines
orthority/param_io.py	81.14%	33 Missing ⚠️
orthority/pan_sharp.py	95.07%	13 Missing ⚠️
orthority/fit.py	85.71%	7 Missing ⚠️
orthority/factory.py	82.75%	5 Missing ⚠️
orthority/camera.py	60.00%	4 Missing ⚠️
orthority/ortho.py	90.62%	3 Missing ⚠️
orthority/cli.py	97.89%	2 Missing ⚠️
orthority/common.py	97.77%	2 Missing ⚠️
orthority/enums.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #15      +/-   ##
==========================================
- Coverage   93.83%   93.05%   -0.79%     
==========================================
  Files          11       13       +2     
  Lines        2205     2734     +529     
==========================================
+ Hits         2069     2544     +475     
- Misses        136      190      +54     

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