Implement tastks REST api
 - Implement REST api for tasks
 - Implement wrappers in arangosh
 - Add API-documentation
 - move unittest from server to common
updated documentation for issue #1074
add Documentation index for the Tasks API
Merge branch 'devel' of github.com:triAGENS/ArangoDB into devel
Rename unittest README to maintainers README, add more information.
Added links to gitbook and markdown-pp
Changed www. to docs. in the README.md for documenation links
issue #1044: added LTRIM, RTRIM
Merge branch 'devel' of https://github.com/triAGENS/ArangoDB into devel
issue #1033: added SPLIT function
issue #1032: added `FIND_FIRST` and `FIND_LAST`
updated CHANGELOG
added `SUBSTITUTE` AQL function
added functions `VALUES` and `ASSEMBLE`
added functions to highlighter
updated documentation
make `CONCAT` and `CONCAT_SEPARATOR` more useful
added tests for accessing _from and _to of a non-edge collection
minor test adjustments
updated docs