Branch choose_tools - commit 1

1. Allow the user to define a file with a list of tools to skip or include
in the compilation.
Branch choose_tools - commit 2

1. Bug fix,
Branch choose_tools - commit 3

1. Bug fix.
Branch choose_tools - commit 4

1. Updated user_settings.json to track the compiled tools.
Branch choose_tools - commit 5

1. When running gkno update, conf is modified to only include the tools in the
user_settings.
Version 0.172 - March 2014

1. Merged in branch choose_tools. When performing the gkno build step, a list of tools
to include can be specified with --compile-tools (-ct) or a list to skip with
--skip-tools (-st). The build process will then only compile the selected tools.
Subsequent use of gkno update will only deal with the compiled tools. The functionality
to add new tools is not yet implemented.