mod_invites_page: Change client selection button text from 'Install' to 'Select' by default This also allows specific clients entries to override the text via the 'select_text' field. Rationale: 1) users may already have the software installed, we still want them to select it anyway for the tailored setup experience. 2) some clients (e.g. web clients) are not really "installed" so the text was misleading

# Introduction

This module sends a [version query][xep0092] to clients when they
connect, and logs the response, allowing statistics of client usage to
be recorded.

Note that since this is per connection, there will be a bias towards
mobile clients on bad connections.

## Example

    info    Running Running Swift version 4.0