Add an option to enable setting a different CacheRoot

[stefannikolei]

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Description

Adding a new Option for the cache implementation. Now the CacheRoot can be set to an different folder than the webroot

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #127 (af70a40) into master (2c5961e) will increase coverage by 0.14%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #127      +/-   ##
==========================================
+ Coverage   88.61%   88.76%   +0.14%     
==========================================
  Files          43       43              
  Lines        1221     1228       +7     
  Branches      144      146       +2     
==========================================
+ Hits         1082     1090       +8     
+ Misses        100       99       -1     
  Partials       39       39              

Flag	Coverage Δ
unittests	88.76% <100.00%> (+0.14%)	⬆️

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

Impacted Files	Coverage Δ
.../ImageSharp.Web/Caching/PhysicalFileSystemCache.cs	97.05% <100.00%> (+0.28%)	⬆️
...harp.Web/Caching/PhysicalFileSystemCacheOptions.cs	100.00% <100.00%> (+100.00%)	⬆️

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[JimBobSquarePants]

If you drop the in modifiers, this looks great. Thanks!

[JimBobSquarePants]

Lovely. Thanks!

I'm planning an official release in a few days but you will be able to grab the build from MyGet in the interim once merged.