moved master argument parsing to CreateSlaveOptions class

Moved the code that validates and parses 'buildbot create-slave'
master argument to runner.CreateSlaveOptions class.
slave cli: replaced Maker class with setupSlaveDirectory() function

No point in creating a single instance of Maker class, we can as well
call a function.
slave cli: added function for creating info/* files

Broke out code for creating buildslave info/admin and info/host files
into a local makeInfo.createFile() function.
catch IO errors when doing 'buildslave create-slave'

When creating buildslave directory with 'buildslave create-slave'
command, catch IO errors and print user friendly error messages.