Initial validation of functions

All template functions contain only 'result' function for resolving
snippet of template. Current patch presents initial implementation of
validate method and support function 'validate' similar to 'resolve'.

Related-Bug: #1273490
Change-Id: Id81493bd72e75da746101c4c741eaf846abd8360
Validation functions for resources and outputs

This patch add ability to validate values in outputs section and also
validate properties in resource snippets.

Related-Bug: #1273490
Change-Id: I9ccb880954751555709bd92f2412cf5606969e70
Merge "Initial validation of functions"
Merge "Validation functions for resources and outputs"