Extend the Unix hosting API
Extend the Unix hosting API

This change modifies the Unix hosting API so that the hosting app can create
as many managed delegates as it needs and execute them as many times it wants.
The new API contains separate functions to initialize and shutdown CoreCLR
and a function to create a delegate.
The current ExecuteAssembly function behavior stays unmodified for now to
ensure that dnx that uses that API and that pulls the binary libcoreclr
is not broken.
After the dnx is updated to use the new coreclr_create_delegate API, I'll remove
the ExecuteAssembly.

Also done:
1) Added support for comments and skipping empty lines in the mscorwks_unixexports.src.
2) Restructured the mscorwks_unixexports.src
3) Added coreclr_execute_assembly to the unixinterface.cpp / exports
4) Modified coreruncommon.cpp to use the new hosting API

kmosher/PowerShell,kmosher/PowerShell,JamesWTruher/PowerShell-1,kmosher/PowerShell,daxian-dbw/PowerShell,bmanikm/PowerShell,jsoref/PowerShell,kmosher/PowerShell,bmanikm/PowerShell,JamesWTruher/PowerShell-1,daxian-dbw/PowerShell,jsoref/PowerShell,TravisEz13/PowerShell,PaulHigin/PowerShell,TravisEz13/PowerShell,KarolKaczmarek/PowerShell,KarolKaczmarek/PowerShell,jsoref/PowerShell,KarolKaczmarek/PowerShell,daxian-dbw/PowerShell,KarolKaczmarek/PowerShell,jsoref/PowerShell,kmosher/PowerShell,bmanikm/PowerShell,PaulHigin/PowerShell,bingbing8/PowerShell,bmanikm/PowerShell,bingbing8/PowerShell,jsoref/PowerShell,PaulHigin/PowerShell,daxian-dbw/PowerShell,bmanikm/PowerShell,TravisEz13/PowerShell,KarolKaczmarek/PowerShell,bingbing8/PowerShell,JamesWTruher/PowerShell-1,PaulHigin/PowerShell,JamesWTruher/PowerShell-1,TravisEz13/PowerShell,bingbing8/PowerShell,bingbing8/PowerShell