NETWORK SERVICE support

1) Fix service profiling by ACLing the shared objects to the service
principal (read/write only is sufficient for the shared memory so far as
the service is concerned)
2) For the case when there may be multiple services running under the
same principal being started concurrently, allow manual selection of
profiler injection to the service environment to be performed for the
service name rather than the service principal.
Update README

Make it repo-specific
Skeleton service running as NETWORK SERVICE

Trival service based on the walkthrough at
http://msdn.microsoft.com/en-us/library/zt39148a%28v=vs.110%29.aspx
Uses Debug.WriteLine rather than Event Log to avoid the need to set
access rights for the relevant keys
Includes PowerShell script for file ACL setting, a script of manual test
steps, and sample coverage output
Tidying up

Remove vestiges of the event log use in the service.
Add trivial unit tests to check that when a service principal is fed in,
appropriately shaped ACLs come out.
Merge branch 'master' of https://github.com/SteveGilham/opencover into SteveGilham-master

Conflicts:
	README.md
Organize code
Merge branch 'SteveGilham-master'