Misc fixes:

* Automatically strip '\' and '/' characters of path and remove tessdata prefix.
* Fixed bug introduced in previous region of interest
* Don't dispose of Pix generated when processing a Bitmap till the Page is disposed off.
Moved change log to root directory.
Added InteropDotNet support
Added additional unit tests and made all Interop related functionality internal.
Fixed regression introduced in last commit

Interop interfaces and Library loader must be public.
Merge branch 'feature/mono-support' into develop
Merge branch 'develop' into dev_3.03

Conflicts:
	Samples/Tesseract.ConsoleDemo/packages.config
	Samples/Tesseract.WebDemo/packages.config
	src/Tesseract.Tests/BaseApiTests.cs
	src/Tesseract.Tests/EngineTests.cs
	src/Tesseract/Internal/Guard.cs
	src/Tesseract/Interop/BaseApi.cs
	src/Tesseract/Interop/LeptonicaApi.cs
	src/Tesseract/Pix.cs
	src/Tesseract/TesseractEngine.cs