Document Field data type used in TH code generation
Document Field data type used in TH code generation

Describe what types of fields are currently possible and allowed and
what what are the types of their "Q Exp" expressions.

Signed-off-by: Petr Pudlak <9d19625f8ee825a2c398462ed335cbcf98f79c32@google.com>
Reviewed-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>

dimara/ganeti,apyrgio/ganeti,mbakke/ganeti,dimara/ganeti,grnet/snf-ganeti,andir/ganeti,andir/ganeti,leshchevds/ganeti,onponomarev/ganeti,ganeti/ganeti,grnet/snf-ganeti,mbakke/ganeti,yiannist/ganeti,onponomarev/ganeti,bitemyapp/ganeti,yiannist/ganeti,ganeti-github-testing/ganeti-test-1,bitemyapp/ganeti,mbakke/ganeti,ganeti-github-testing/ganeti-test-1,andir/ganeti,leshchevds/ganeti,yiannist/ganeti,apyrgio/ganeti,ganeti/ganeti,ganeti/ganeti,leshchevds/ganeti