Make sure that a template is unique

[dilshat]

Only one template exists for a single combination of name, owner and version. The combination of name+owner+version is a unique composite key for a template which can be used interchangeably with ID

[emli]

Duplicated https://github.com/subutai-io/cdn/issues/220

[dilshat]

@emli no this is now a bit different. Issue https://github.com/subutai-io/cdn/issues/220 was valid before multiversion support was introduced No we have to stick to the logic described above

[dilshat]

About uploading a template with the same key (name+owner+version): If a template with such key already exists then upload must fail and be allowed only if new version is higher

[kurmanbekova6]

Fixed on Master