speech vendor names should be case insensitive

[sammachin]

Currently the vendor name in recogniser and synthisizer objects is case sensitive, by default all the built in providers we use lower case eg google microsoft however the lables in the web UI are capitalised.
This can lead to confusion when a developer capitalises the name in their verbs, and being a vendor name it is quite natural to capitalise it.

It is also hard to debug the errror as the alert message just says credentials not provided for $vendor name, see image

To avoid issues I think we should just .lowerCase the field on input.