Adds information about regular expressions for Compute API

- when searching for a name, regexp is used for server name,
not xsd:string.
- hoping to convey this difference with a paragraph as well
as changing xsd:string to regexp in the parameter table.

Closes-bug: 1365227
Change-Id: Idd8bea413ab4581e495cd4ee58d4a2d8554e62bc
Merge "Adds information about regular expressions for Compute API"