oeqa: fix hasPackage, add hasPackageMatch

oeqa: fix hasPackage, add hasPackageMatch

hasPackage() was looking for the string provided as an RE substring in the
manifest, which resulted in a large number of false positives (i.e. libgtkfoo
would match "gtk+").

Rewrite the manifest loader to parse the files into a proper data structure,
change hasPackage to do full string matches, and add hasPackageMatch which does
RE substring matches.

Signed-off-by: Ross Burton <ross.burton@intel.com>