Cleaning up the network layer, refactored NetworkThread..

[adamhass]

This PR mainly restructures the NetworkThread to make it a bit more pleasant to work with/look at.
I'd prefer to merge it now so as to avoid potential merge conflicts later on when I actually add more stuff on top...

Improved error handling and added unwinding of the NetworkThread in net/mod.rs, I'm unsure if I'm doing it properly there but I think it should make for some nicer log messages if/when the NetworkThread panics.

Also made some more updates to the docs page for network buffers.

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Issues

Reference or describe the issues this PR addresses.

[adamhass]

I'll force-push the cargo fmt after this PR has been merged: bheisler/TinyTemplate#17

[codecov]

Codecov Report

Merging #141 (a364dbd) into master (11c463a) will increase coverage by 1.20%.
The diff coverage is 81.76%.

@@            Coverage Diff             @@
##           master     #141      +/-   ##
==========================================
+ Coverage   70.68%   71.89%   +1.20%     
==========================================
  Files          90       92       +2     
  Lines       15844    16445     +601     
==========================================
+ Hits        11200    11823     +623     
+ Misses       4644     4622      -22     

Impacted Files	Coverage Δ
core/src/actors/mod.rs	90.00% <ø> (ø)
core/src/lib.rs	91.34% <ø> (ø)
core/src/utils/mod.rs	53.70% <ø> (+4.61%)	⬆️
docs/examples/src/bin/bootstrapping.rs	0.00% <0.00%> (ø)
docs/examples/src/bin/dns_resolver.rs	0.00% <0.00%> (ø)
docs/examples/src/bin/load_balancer.rs	0.00% <0.00%> (ø)
docs/examples/src/bin/serialisation.rs	0.00% <0.00%> (ø)
core/src/routing/mod.rs	97.87% <50.00%> (-0.01%)	⬇️
core/src/default_components.rs	87.69% <55.55%> (-1.97%)	⬇️
core/src/dispatch/mod.rs	78.92% <66.29%> (+0.68%)	⬆️
... and 37 more

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