#119 Initialization of Content's AutoHidePortion

When a DockContent is docked left, right, top, or bottom, the
AutoHidePortion will be initialized to the value of the respective
area's portion.  This allows the AutoHide to take on a fixed-size sizing
whereas previously it would always use a percentage sizing, starting at
25%.
Made undenoted sln the most recent VS version

We're versioning off old solution files for past versions of Visual
Studio (even though it's easy to change, there are no material structure
changes), but have been leaving the "plain" solution file as the old
VS2008 version.  Rather than explicitly version the current version, let
the "plain" version be the current solution file, with old versions
denoted in the file name.
#115 - Remove use of tabs for indentation

There's religion, politics, and tabs vs spaces.  Regardless of your view
it should be consistent, and since I'm implementing the change we're
going spaces.  If we need justification beyond my personal preference,
this is the default in Visual Studio.
#81 - Add ActiveAutoHideContentChanged event

Added pull request from lockszmith to add an event to the DockPanel that
will be raised when the value of the AutoHideWindow's ActiveContent
property changes.
#123 - Require click to show autohide content

Opt-in feature to require a tab to be clicked on to show autohide
content vice the current behavior of showing on hover.
Fixed compilation.
Revert "Fixed dock windows size calculation to avoid crash on Mono/Linux."

This reverts commit 477c28ac6aabd5e07515b0cc4a405ec5ac1e4997.