Update readme and scripts

Both bootstrap and singleheader now name the files the same as the library's default.
Output now directed toward gen directory for the corresponding dir (project, singleheader, or test)

scripts/singleheader.ci.ps1

@@ -16,6 +16,7 @@ foreach ( $arg in $args )
 $path_root               = git rev-parse --show-toplevel
 $path_singleheader       = Join-Path $path_root singleheader
 $path_singleheader_build = Join-Path $path_singleheader build
+$path_singleheader_gen   = Join-Path $path_singleheader gen
 
 write-host "`n`nBuilding gencpp bootstrap`n"
 
@@ -41,6 +42,10 @@ Push-Location $path_root
 Pop-Location
 
 Push-location $path_singleheader
+if ( -not(Test-Path($path_singleheader_gen) )) {
+	New-Item -ItemType Directory -Path $path_singleheader_gen
+}
+
 # Run meta-program
 $gencpp_singleheader = Join-Path $path_singleheader_build gencpp_singleheader.exe