find_in_models: Search the entire block diagram hierarchy

A wrapper for find_system which searches inside model references

find_system provides the option to search inside library links, but does not currently give the option to search inside model references.
This function provides this option, and, unlike find_system itself, can also close block diagrams after searching them. This ensures scalability when searching large hierarchies. The usage is very similar to that of find_system itself except that a model name or handle must be specified. The return type also depends on the inputs in the same way as for find_system: specifically the return type is a cell array of strings unless the input is a numeric handle ot the "FindAll" option is supplied and "on".

When the return type is a cell array of strings, any block diagrams which are loaded during the search are closed again. This means that the caller must take care before calling get_param on any returned string. It also means that the model does not need to be loaded before calling this function.

This function can be used for tasks such as:
* Finding all the Lookup Table blocks involved in a simulation
* Finding any models involved a simulation which have some parameter value
* Finding all lines in a simulation which link to a particular requirement
etc.

See the Help in the M-file for examples.