Update build to be more consistent no matter how you build it.

This is the initial change to switch to using common targets across the repo.

This change adds a dir.props and dir.targets file that each project file will
import at the top and bottom of the project to default a lot of the common properties
and targets.
Update the newly added projects to import dir.props/dir.targets.
Clean up some of the dir.props and dir.targets files.

Add a VerifyBuildTools target to dirs.proj to ensure check for build tools
before trying to build. I tried adding something similar to dir.targets but
there was some issues and it seemed to cause some perf hits checking in ever
project build. If we find that we run into issues we can reconsider adding that.

This change also updates build.proj to add a semaphore file to use to detect
if build tools have been installed or not.
Add dir.props/dir.targets to all the test projects and enable building them.

Added */tests/*.csproj file to dirs.proj list of projects to build.

There are some tests like the MetadataReaderTests that build against desktop
framework and so that project needed some hacking to get the correct props used,
we should fix that at another point.
Rename the System.Linq.Parallel test folder from "test" to "tests" to follow
the convention.
Remove mscorlib reference from System.Linq.Parallel.Tests.csproj.

The mscorlib reference is no longer needed as it is automatically added
by dir.targets now.
Clean up some project files for to improve consistency and spacing.
Remove the old TFS source bindings from the props file as it isn't needed with git.
Fix System.Linq.Parallel.sln file after move of the test project.
Switch to importing dir.props/dir.targets using GetDirectoryNameOfFileAbove.

This commit also updates the new System.IO.Pipes.csproj to follow the pattern.
Add PackagesDir to the clean target in build.proj
Fix up a few bad merges and add settings that moved across files.
Disable some xpath AxesCombination tests that fail on debug.

File issue 284 to track fixing these fixes. Now that we switched to debug
builds by default these started failing.
Fix newly added FileVersionInfo project to have dir.props/targets.
Merge pull request #261 from weshaggard/ConsistentBuild

Enable consistent builds by sharing common properties and targets
CLEANUP - Removed unused namespace references.
Merge pull request #273 from IAmAnubhavSaini/master

Remove some unused using statements in console.cs.
System.Numerics.Vectors.sln: use correct configuration for Debug

Before, the Release target got incorrectly assigned to the Debug configuration
for the library and test projects. This results in the library being compiled
into the Release dir when the solution is compiled on the command line
via msbuild.exe, while it should be compiled into the Debug dir.
dir.props: correctly enclose 'Exists' condition in single quotes

According to MSDN (http://msdn.microsoft.com/en-us/library/7szfhaft.aspx), the
single quotes can be left off for "simple alphanumeric strings or boolean values".
This is not the case here (it is a property), so we should use single quotes.

Note that MSBuild ignores this, but it results in a parser error on Mono's xbuild.
Merge pull request #286 from akoeplinger/patch-2

dir.props: correctly enclose 'Exists' condition in single quotes