microkernel -> unikernel

And a few other assorted typo fixes.  Closes #220
bump to 1.1.1 working version
Merge pull request #223 from avsm/master

man page and README fixes
Activate backtrace recording by default

Closes #225
Merge branch 'master' of github.com:mirage/mirage
Fixes in the `V1.STACKV4` to expose UDPv4/TCPv4 types properly

Closes #226
[lib] tweak block and vif lines in sample `.xl` to be more correct