Various quality of life improvements

[tpoisot]

What the pull request does

• [x] Adds an overload to collect to get the non-nothing values. (Fixes #48)
• [x] ~Adds an overload to isnothing to get the coordinates of nothing values~
• [x] Adds an overload to hcat and vcat (Fixes #49)
• [x] Adds a new similar method (Fixes #47)
• [x] Adds a mask function to clip a layer using a Boolean layer

Type of change

Please indicate the relevant option(s)

• [x] :sparkle: New feature (non-breaking change which adds functionality)
• [x] :book: This change requires a documentation update

Checklist

• [x] The changes are documented
  • [x] The docstrings of the different functions describe the arguments, purpose, and behavior
  • [x] There are examples in the documentation website
• [x] The changes are tested
• [x] The changes do not modify the behavior of the previously existing functions
• [x] The Project.toml field version has been updated

[codecov-io]

Codecov Report

Merging #50 (f899850) into master (1a41008) will increase coverage by 1.29%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #50      +/-   ##
==========================================
+ Coverage   85.75%   87.05%   +1.29%     
==========================================
  Files          17       17              
  Lines         344      363      +19     
==========================================
+ Hits          295      316      +21     
+ Misses         49       47       -2     

Flag	Coverage Δ
unittests	87.05% <100.00%> (+1.29%)	:arrow_up:

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

Impacted Files	Coverage Δ
src/datasets/geotiff.jl	100.00% <100.00%> (ø)
src/lib/overloads.jl	94.44% <100.00%> (+4.30%)	:arrow_up:
src/recipes/recipes.jl	88.23% <100.00%> (ø)

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[tpoisot]

@gabrieldansereau you might be right - I think we can remove it and use an iterator as suggested by @mkborregaard in #51, to do something with findall instead. I should be able to remove it without too much trouble.