Add a command to list available templates

[damyanpetev]

Since the number of templates has grow quite a bit, it won't be reasonable to list them in readme/docs.
It'll be better if there's a command that can list all available templates, filtered by framework [and project].

[wnvko]

After internal discussion the command should work in this way:

• if one is not in a project command without parameters should list all available templates by product group;
• if one is not in a project command with framework and type specified should list all templates for this specific framework/type by product group;
• if one is in a project command should list all templates by product group, related to the framework/type the project was generated for.

List command should be available only as alone command. It should not be a part of other commands, e.g. wizard, new, add and so on.