Add basepath to base uri and asset paths

[frankdekker]

Q	A
Type	bugfix
Issue	Resolves #297
Breaking change	no

In the case the symfony project is deployed in a basepath, the indicated base-uri and asset path should take into account the difference in location of assets.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (e99c438) to head (d9e9d33).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##              master      #301   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity       472       472           
===========================================
  Files             95        95           
  Lines           1233      1234    +1     
===========================================
+ Hits            1233      1234    +1     

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