speed up instanciation of v8 ShapedJson objects

now a static buffer is used to create multiple string values
such as `_id`, `_key`, `_rev`, `_from` and `_to`.
this saves a few memory allocations per document
do not complain about missing dispatcher when server is started with `--no-server` option
added `type` option for `GET /_api/document?collection=...`

Conflicts:
	CHANGELOG
removed hard-coded value
take compatibility settings into account even for async requests
Merge branch 'devel' of https://github.com/triAGENS/ArangoDB into aql2

Conflicts:
	arangod/Utils/CollectionNameResolver.h
	arangod/V8Server/v8-vocbase.cpp