refactor(solutions): renamed solution files to DayXX.cs; no changes to namespace or classes

Author: sindrekjr

AdventOfCode/Solutions/Year2019/Day01/Solution.cs renamed to AdventOfCode/Solutions/Year2019/Day01/Day01.cs

@@ -39,7 +39,7 @@ if(!(Test-Path $newDirectory)) {
 }
 
 for($i = 1; $i -le 25; $i++) {
-    $newFile = Join-Path $newDirectory "Day$("{0:00}" -f $i)"  "Solution.cs"  
+    $newFile = Join-Path $newDirectory "Day$("{0:00}" -f $i)"  "Day$("{0:00}" -f $i).cs"
     if(!(Test-Path $newFile)) {
         New-Item $newFile -ItemType File -Value ($template -replace "<YEAR>", $Year -replace "<DAY>", "$("{0:00}" -f $i)") -Force | Out-Null
     }