Improved CharacterAnalyzer

* space + tab is called "White" in the 1.2 spec
* Used the more precise name IsAlphaNumericDashOrUnderscore
* Merged methods by using default parameter values
Improved EventReader

* Changed some naming
* Made use of ParsingEvent.NestingIncrease
Improved SimpleKey

* Removed docs since it is non-public
* Now sets SimpleKey.Mark to Mark.Empty in default ctor
Improved StringLookAheadBuffer

* Minor code changes
Improved TagDirectiveCollection and Version

* Minor code changes
Turned the Mark into a value class and added Cursor as a factory class

.. since changing a Mark makes no sense outside of Scanner
Merge pull request #76 from rogernorling/cursor-mark

Mutable Cursor, immutable Mark
Merge pull request #77 from rogernorling/code-improvement

Conflicts:
	YamlDotNet/Core/Scanner.cs
Make Line and Column properties of Mark start at one instead of zero.
Add performance tests for the current version.
Fix performace problem in CharacterAnalyzer.Check().
Slightly improve ReflectionPropertyDescriptor.

A refactoring is needed to separate the metadata part of IPropertyDescriptor from the getter and setter so that the metadata can be cached.
Cleanup project and solution configurations.