added string-include

added a few functions to templ/diet.d and a hook to it in server.d
Merge branch 'string-include'
added a ddoc to compileStringIncludeDietFile
you can now import a stringTemplate as ALIAS

I guess it looks even more ugly than yesterday
but
compileStringIncludeDietFile can now be called like this
("templ.td",somevar,string-tmpl);
and you can include it with: include #{string-tmpl}
missed to commit this ...

I'm working with vibe-0.7.17 ... so pushing to master is .... difficult
to get right ...
Multiple String-imports per file are now supported.

this however involved adding a template form bearophile I found while
searching for directions
I reverted my changes to the exsisting templates.
I think this is now mergeable...
pure breaks compile
Merge pull request #1 from UplinkCoder/master

pull request for string-include