Disable reflection option

[tgiphil]

When reflection is disabled, the reflection metadata could be excluded to save memory.

This would be extremely valuable and necessary for low memory platforms.

[charsleysa]

Just a note, this may possible affect the use of generics as some code may possibly need reflection Metadata for some generics to work properly. (AFAIK we still have an incomplete generics implementation).

[charsleysa]

Related: #331

[tgiphil]

1. Added compiler option (--disable-reflection) to indicate if reflection will be supported.

2. Update MetadataStage.cs so that only data structures required functionality to support RTTI are emitted.

3. Items not emit:

• Names
• Properties
• Fields
• Parameters
• Custom Attributes
• Assemblies

4. Reorder Method definition fields so that RTTI information is first. That way the method definition entry can be truncated when reflection support is not enabled.

5. Exclude methods that enable reflection. (Note: The method scanner may excluded some of this).

6. Add flag to indicate to the runtime that reflection is disabled (and metadata may be missing)