#342 Suppport for Env Variables in Tab title

[mfurtado]

Request: Support the tab title config item to hold environment variables
Example: Setting the tab titles to equal "%USERNAME%@%DOMAIN%" to display John@Acme

Motivation: This would greatly increase flexibility of a dynamic title where certain information may be important to distinguish, ie having 2 console windows running under different user contexts, currently would need to manually change the tab title every time in order to know which user is it running under. Without having to install multiple console executables.