Fix DataRow error management

DataRow's RowError is supposed to be String.Empty to indicate
no errors, but is sometimes wrongly set to null, falsely indicating
errors. Fixed to be String.Empty.
Added test for DataRow error
Test uses SQLite in-memory DB for test

Also spaces to tabs
[monodoc] Changes to support new-style iOS documentation:

- Fixed bug in creating CREF strings.
- Refactored XML file processing for customization during new style iOS assembly. This was done through the new file source interface, which lets you use dependency injection to customize the process.
- Added the ability to rewrite CREF references when assembling docs that use native types. Also, the ability to handle dropped namespaces.
[mdoc] Changes to support new-style iOS API:

- the dropns flag now lets you define a namespace that is dropped in a new version of the assembly during update.
- the ntypes flag lets you tell the update command that certain methods are now using native types, and as such will attempt to match with old types in order to preserve documentation.
- the preserve flag will avoid removing members. This is to avoid dropping documentation for members that changed from one version of the framework to another new-style version (ie. iOS).
Correct code review comments on test
[Cleanup] Removed .jvm.cs files that are no longer used

They were once part of a special Java target profile, but this is no longer used today.
[Cleanup] Removed net_1_1_java*.sources files

They were once part of a special Java target profile, but this is no longer used today.
[Cleanup] Removed net_1_1_java from Makefiles

It was once part of a special Java target profile, but this is no longer used today.
[Cleanup] Removed JavaEE csproj and sln files

They were once part of a special Java target profile, but this is no longer used today.
[Cleanup] Removed files that imported Java namespaces

They were once part of a special Java target profile, but this is no longer used today.
[Cleanup] Removed TARGET_JVM

It was once part of a special Java target profile, but this is no longer used today.
[mdoc] Added preserver.cs to build script so make compiles
[mdoc] Fixed an issue with type-file path resolution.
In certain cases, such as stubbing out namespace-less classes it was failing to produce the right paths.
[mdoc] Fixed issue with assembly versions being added incorrectly
[mdoc] Moved enumeration back into deferred mode.
This resolved an issue with the ecmadoc importer that assumed execution would be deffered in order to keep reading from the XmlReader
[mdoc] Style updates per pull request feedback
[mdoc] Changed 'old' and 'new' to 'classic' and 'unified' per feedback.
[Sgen] Transport scan macros from sgen-descriptor.h to sgen-scan-object.h

This commit transport the scan macro from sgen-descritor.h to
sgen-scan-object.h. This is useful for modify at compile time
the scan macro according to the scan function.

I release this change under the MIT license.
[Sgen] Implement partial marking for big array of objects

This commit changed the gray stack to support work items. When a big
array of objects is marked, Sgen now create several work items. Every
work item rappresents a pieces of the array that must be scanned.
Since they are different pieces, the workers can now parallel scan
and mark the array, resulting in a better work distribution between
the workers.

I release this change under the MIT license.