Make possible to change the lg template manager in the runtimes to allow a better multilanguage managemet

[guru98]

The structure of the responses propose in composer is inefficient in general and more in multilanguages bots. Specifically if you use actions templates and adaptive cards you have to repeat them for every languages evenif are the same. My suggestion is: allow, at ui level, to save adaptive card json in files to be reused on every language Allow to use a custom template manager derived from multilanguagelg where we can implement a smarter gerarchie between lg files. The idea is to have: an activities.lg file and adaptivecards files common for every language and manage to have specific language files for labels. text response,etc. Without a custom multilanguagelg template manager this is not possible