Improve setup of examples

[devmotion]

This PR separates the configuration of examples and how they are built more cleanly from the rest of the documentation. Currently, at build time environments are nested and hence not cleanly separated. Moreover, with the PR examples are run in parallel.

The same setup is used e.g. in AbstractGPs.jl and KernelFunctions.jl.

[codecov-commenter]

Codecov Report

Merging #125 (939b892) into master (d005664) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #125   +/-   ##
=======================================
  Coverage   97.67%   97.67%           
=======================================
  Files          13       13           
  Lines         687      687           
=======================================
  Hits          671      671           
  Misses         16       16           

Impacted Files	Coverage Δ
src/exact.jl	92.66% <ø> (ø)

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[coveralls]

Pull Request Test Coverage Report for Build 1178704008

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 97.671%

---

Totals
Change from base Build 1178364664:	0.0%
Covered Lines:	671
Relevant Lines:	687

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 1178026320

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 97.654%

---

Files with Coverage Reduction	New Missed Lines	%
src/exact.jl	1	92.66%
<!--	Total:	1		-->

Totals
Change from base Build 1174249145:	0.0%
Covered Lines:	666
Relevant Lines:	682

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 1178006528

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 97.654%

---

Files with Coverage Reduction	New Missed Lines	%
src/exact.jl	1	92.66%
<!--	Total:	1		-->

Totals
Change from base Build 1174249145:	0.0%
Covered Lines:	666
Relevant Lines:	682

---

💛 - Coveralls