Clean up build scripts

Decompose into self-contained granular components
Provide reasonable defaults for cross cutting concerns, allowing for independent execution of steps
Start unifying Windows/Bash architecture

fix Bash CI scripts

dockerbuild.sh _common.sh path

Add missing restore-packages.sh

Copy/paste issues

Quote $SOURCE
fix .gitignore

PR Feedback

Merge in @SridarMS's work to avoid redownloading DNX

enabling build of dotnet-build

merge in @SridharMS's CentOS changes

Enable building FSC

enable restoring specific subdirectories

Fix dnx version check

Add missed dependency

Fix pathing to tests

Match Linux build version to Windows, fixing linux tests as a side effect.

workaround for coreclr#2215

fix pathing issue

disable building in docker

BUILD_IN_DOCKER was set, somehow...

fix headers

scripts/obtain/install.ps1

@@ -0,0 +1,91 @@
+#
+# Copyright (c) .NET Foundation and contributors. All rights reserved.
+# Licensed under the MIT license. See LICENSE file in the project root for full license information.
+#
+
+$ErrorActionPreference="Stop"
+$ProgressPreference="SilentlyContinue"
+
+$Feed="https://dotnetcli.blob.core.windows.net/dotnet"
+$Channel="dev"
+$DotNetFileName="dotnet-win-x64.latest.zip"
+$DotNetUrl="$Feed/$Channel/Binaries/Latest"
+
+function say($str)
+{
+    Write-Host "dotnet_install: $str"
+}
+
+$InstallDir = $env:DOTNET_INSTALL_DIR
+if (!$InstallDir) {
+    $InstallDir = "$env:LocalAppData\Microsoft\dotnet"
+}
+
+say "Preparing to install .NET Tools to $InstallDir"
+
+# Check if we need to bother
+$LocalFile = "$InstallDir\cli\.version"
+if (Test-Path $LocalFile)
+{
+    $LocalData = @(cat $LocalFile)
+    $LocalHash = $LocalData[0].Trim()
+    $LocalVersion = $LocalData[1].Trim()
+    if ($LocalVersion -and $LocalHash)
+    {
+        $RemoteResponse = Invoke-WebRequest -UseBasicParsing "$Feed/$Channel/dnvm/latest.win.version"
+        $RemoteData = @([Text.Encoding]::UTF8.GetString($RemoteResponse.Content).Split([char[]]@(), [StringSplitOptions]::RemoveEmptyEntries));
+        $RemoteHash = $RemoteData[0].Trim()
+        $RemoteVersion = $RemoteData[1].Trim()
+
+        if (!$RemoteVersion -or !$RemoteHash) {
+            throw "Invalid response from feed"
+        }
+
+        say "Latest version: $RemoteVersion"
+        say "Local Version: $LocalVersion"
+
+        if($LocalHash -eq $RemoteHash)
+        {
+            say "You already have the latest version"
+            exit 0
+        }
+    }
+}
+
+# Set up the install location
+if (!(Test-Path $InstallDir)) {
+    mkdir $InstallDir | Out-Null
+}
+
+# De-powershell the path before passing to .NET APIs
+$InstallDir = Convert-Path $InstallDir
+
+say "Downloading $DotNetFileName from $DotNetUrl"
+$resp = Invoke-WebRequest -UseBasicParsing "$DotNetUrl/$DotNetFileName" -OutFile "$InstallDir\$DotNetFileName"
+
+say "Extracting zip"
+
+# Create the destination
+if (Test-Path "$InstallDir\cli_new") {
+    del -rec -for "$InstallDir\cli_new"
+}
+mkdir "$InstallDir\cli_new" | Out-Null
+
+Add-Type -Assembly System.IO.Compression.FileSystem | Out-Null
+[System.IO.Compression.ZipFile]::ExtractToDirectory("$InstallDir\$DotNetFileName", "$InstallDir\cli_new")
+
+# Replace the old installation (if any)
+if (Test-Path "$InstallDir\cli") {
+    del -rec -for "$InstallDir\cli"
+}
+mv "$InstallDir\cli_new" "$InstallDir\cli"
+
+# Clean the zip
+if (Test-Path "$InstallDir\$DotNetFileName") {
+    del -for "$InstallDir\$DotNetFileName"
+}
+
+say "The .NET Tools have been installed to $InstallDir\cli!"
+
+# New layout
+say "Add '$InstallDir\cli\bin' to your PATH to use dotnet"