Create a PS1/BAT script to install Python and the EBCLI

The PS1 script invokes:
- install-python.ps1
- ebcli_installer.py if the Python installer exists with code 0

The PS1 script installs instructs ebcli_installer.py to install `eb` in
the user's home directory (within a .ebcli-virtual-env folder).

The BAT script wraps the PS1 script.

Author: rahulrajaram

scripts/bundled_installer.bat

@@ -0,0 +1 @@
+Powershell.exe -executionpolicy remotesigned -File "%~dp0\bundled_installer.ps1"

scripts/bundled_installer.ps1

@@ -0,0 +1,57 @@
+function Write-OutputWithInvertedColors([String] $Message) {
+    Write-Host $Message -ForegroundColor Black -BackgroundColor White
+}
+
+function Get-HomePath() {
+    if (Test-Path Env:\USERPROFILE) {
+        return $env:USERPROFILE
+    } elseif (Test-Path Env:\HOMEDRIVE -and Env:\HOMEPATH) {
+        return $env:HOMEDRIVE + $env:HOMEPATH
+    } elseif (Test-Path Env:\LOCALAPPDATA) {
+        return $env:LOCALAPPDATA
+    } elseif (Test-Path Env:\APPDATA) {
+        return $env:APPDATA
+    } else {
+        Write-Host "Cannot determine user's home directory." -ForegroundColor Red
+        Exit 1
+    }
+}
+
+function Exit-OnFailure() {
+    if ($LASTEXITCODE -ne 0) {
+        Write-Host "Exiting due to failure" -ForegroundColor Red
+        exit 1
+    }
+}
+
+function Update-UserEnvironmentPath {
+    $env:Path =
+        [System.Environment]::GetEnvironmentVariable("Path","Machine") +
+        ";" +
+        [System.Environment]::GetEnvironmentVariable("Path","User")
+}
+
+function Write-StepTitle([String] $Message) {
+    $equals = "=" * 46
+    Write-Host ""
+    Write-OutputWithInvertedColors $equals
+    Write-OutputWithInvertedColors $Message
+    Write-OutputWithInvertedColors $equals
+}
+Write-StepTitle "I. Installing Python                          "
+powershell "$PSScriptRoot\install-python.ps1"
+Exit-OnFailure
+Update-UserEnvironmentPath
+
+Write-StepTitle "II. Creating self-contained EBCLI installation"
+$HomeDir = Get-HomePath
+Write-Host "Installing the EBCLI in $HomeDir\.ebcli-virtual-env"
+python "$PSScriptRoot\ebcli_installer.py" --virtualenv-executable "$PSScriptRoot\virtualenv\bin\virtualenv.exe" --hide-export-recommendation --location $HomeDir
+Exit-OnFailure
+
+$PathExporter = "$HomeDir\.ebcli-virtual-env\executables\path_exporter.vbs"
+if ([System.IO.File]::Exists($PathExporter)) {
+    Write-StepTitle "III. Exporting `eb` PATH's                    "
+    & "$HomeDir\.ebcli-virtual-env\executables\path_exporter.vbs"
+    Update-UserEnvironmentPath
+}