Update CONTRIBUTING.asciidoc

Adding in information from the wiki.
Merge pull request #486 from LightGuard/patch-1

Update CONTRIBUTING.asciidoc
FORGE-1929: Created command to generate CrossOriginResourceSharingFilter
FORGE-1929: Fixed category name
FORGE-1929: Added description to inputs
FORGE-1929: Reordered inputs
Added description in AbstractJavaSourceCommand inputs
Minor correction
Update README.asciidoc
FORGE-1892 Convert contentType option to multiple input.

This ensures that multiple content types can be added.
Also, custom content-types can be specified.
FORGE-1925 Assign user input values to UIInputMany fields.
Merge pull request #484 from VineetReynolds/FORGE-1892

FORGE-1892 and FORGE-1925