Clarify regular expression syntax

[hwellmann]

Clarify which flavour of regular expression syntax is supported by the pattern facet.

[petrochenko-pavel-a]

It is same as in http://json-schema.org/latest/json-schema-validation.html#anchor6

[freddrake]

This needs to be spelled out in the RAML spec. This can't be left as a tooling issue.

[sichvoge]

@petrochenko-pavel-a feel free to provide a PR.

[sichvoge]

Where would you guys add these information? I assume these are the same for pattern properties and for the pattern facet, right @petrochenko-pavel-a?

[sichvoge]

The link to the specific JSON Schema spec part should rather be http://json-schema.org/latest/json-schema-validation.html#rfc.section.3.3

[jagadeesh-mri]

@petrochenko-pavel-a feel free to provide a PR.

I have provided a pull request at #723. Please review and approve

[jagadeesh-mri]

The link to the specific JSON Schema spec part should rather be http://json-schema.org/latest/json-schema-validation.html#rfc.section.3.3

I have added this information into RAML documentation and created a pull request here #723. Please review and approve so that it can go to master branch