Rename support

[rummatee]

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This PR attempts to implement the rename function. Therefore it implements #21 . There are however still some limitations: If there isn't a reference in the same file, as the definition, the definition doesn't get changed. Also at least in my editor (nvim) it is only possible to do one rename and it's necessary to restart before doing the next rename. I would appreciate any help with these issues or any further comments.

[codecov[bot]]

Codecov Report

Merging #768 into master will decrease coverage by 1.05%. The diff coverage is 52.7%.

@@             Coverage Diff              @@
##             master     #768      +/-   ##
============================================
- Coverage     82.12%   81.07%   -1.06%     
- Complexity      935      955      +20     
============================================
  Files            44       44              
  Lines          2154     2219      +65     
============================================
+ Hits           1769     1799      +30     
- Misses          385      420      +35

Impacted Files	Coverage Δ	Complexity Δ
src/Definition.php	100% <ø> (ø)	6 <0> (ø)	:arrow_down:
src/Index/Index.php	75% <0%> (-2.42%)	56 <0> (+2)
src/Factory/LocationFactory.php	100% <100%> (ø)	2 <1> (+1)	:arrow_up:
src/DefinitionResolver.php	87.58% <100%> (+0.12%)	335 <0> (+3)	:arrow_up:
src/Server/TextDocument.php	64.83% <44.64%> (-10.73%)	71 <36> (+14)

[rummatee]

I rewrote the definition finding and added code to update the index after the rename. The issues I described earlier should be solved with this.