adding LaunchXcodebuildTaskAndFeedEventsToReporters()

... which knows how to launch an NSTask that's spewing xcodebuild
output, and then push that output to the reporters.
TitleKey should be defined as 'title' and not 'command'

copy/paste error :-(
renaming 'build_tests_temp' to 'Tests'

... mostly for cosmetic reasons so I can see...

```
=== BUILD-TESTS ===

  xcodebuild build Tests
    TestProject-Library / TestProject-Library (Debug)
      ✓ Check dependencies (56 ms)
```

... in my terminal instead of ...

```
=== BUILD-TESTS ===

  xcodebuild build build_tests_tmp
    TestProject-Library / TestProject-Library (Debug)
      ✓ Check dependencies (56 ms)
```
let's have most of our xcodebuild calls go through the same function...

It will handle sending the 'begin-xcodebuild' event, running xcodebuild
while feeding all the events to the reports, and following up with the
'end-xcodebuild' event.
when xcodebuild fails, print the same error message xcodebuild would show.

Previously, we'd tell you nothing.  Now we'll show something like...

```
=== CLEAN ===

  xcodebuild clean ProjectsWithDifferentSDKs
    OSXLibrary / OSXLibrary (Debug)
      ✓ Check dependencies (50 ms)
      ✓ Remove OSXLibrary.build (1 ms)
      ✓ Remove OSXLibrary.dylib (1 ms)
      ✓ Remove OSXLibrary-Prefix.pch.pth (1 ms)

    iOSLibrary / iOSLibrary (Debug)

  xcodebuild clean Tests
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Failed to build workspace Tests with scheme Tests.
Reason: Scheme "Tests"Tests is not configured for running.
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

** CLEAN FAILED ** (986 ms)
```