small usability improvements for starting the keymapper the first time (or on a new distro :)

[kbilsted]

instaling keymapper on linux (first time), works out the box. nice!

after a reboot i see a popup that keymapper could not find the config file. I followed the install guide in the readme but it never told me where to store the file.

1. it would be nice to be told the path and name so i can easily move the config accordingly or know where to edit
2. the message could also suggest to use the popup menu "configuration" (new users may not know about it).
3. a further improvement. To support people storing configs in git, is to with the installation, to install a standard configuration file. this cna be opened using the gui "configuration" popup..the file should contain only a comment at the top telling

# if you want your configuration placed in a different location (perhaps you clone it from github).
# simply add the following line:
# 
# @include "~/src/myconfigs/keymapper/keymapper.conf"

or add to the install section of the readme - to give new users a head start